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I 


PAPER 
TESTING  METHODS 

Microscopical,  Chemical^  and  Physical  Processes 

Described,  with  the  Apparatus 

Employed 


By 

Committee  on  Paper  Testing 

Technical  Association  of  the  Pulp  and 
Paper   Industry 


Price  $3.00 

Published  by  the 

Technical  Association  of  the  Pulp  and  Paper  Industry 

18  East  41st  Street,  New  York  City 
1922 

(Reprinted  1924) 


The  following-  list  of  books  and  pamphlets  consists  of  works  which  should  be 
on  the  desk  or  in  the  library  of  every  paper  mill  executive.  It  includes  the  best 
works  dealing  with  American  practice,  with  a  few  of  European  origin  that  will  be  of 


general  interest. 

HISTORY  OF  PAPER  MANUFACTURING 
IN  THE  UNITED  STATES,  by  Lyman 
Horace  Weeks  (1916).  An  account  of  the 
origin  and  development  of  paper  manufac- 
ture in  the  United  States  from  1690  to  1916. 
(  Lockwood  Trade  Journal  Co.,  10  East  39th 
St..  New  York.  $6.) 

PULPWOOD  AND  WOOD  PULP,  by  Royal 
S.  Kellogg  (1923).  A  short  treatise  on  the 
basic  raw  material  for  paper  with  statistical 
data  on  production  and  consumption  in 
North  America.  (  McGraw-Hill  Book  Co., 
370  Seventh  Ave..  New  York,  $4.) 

MANUFACTURE  OF  PULP  AND  PAPER, 
in  five  volumes,  edited  by  J.  N.  Stephenson. 
Vols.  I  and  II  deal  with  the  sciences  in  their 
relation  to  the  manufacture  of  pulp  and 
paper  (1921).  Vol.  Ill,  Preparation  and 
Treatment  of  Wood  Pulp  (1922).  Vol.  IV. 
Preparation  of  rags  and  waste  papers  ;  beat- 
ing, sizing  and  coloring;  paper  machines. 
Vol.  V,  in  preparation  (to  be  issued  in  1924). 
Manufacture  of  paper  and  general  mill  equip- 
ment. (Technic  .ciation  of  the  Pulp 
and  Paper  Industry.  IS  East  41st  St., 
York,  $5  per  vol.  McGraw-Hill  Book  Co., 
publishers.) 

MODERN  PULP  AND  PAPER  MAKING, 
by  G.  S.  Witham,  Sr.  (1920).  A  practical 

in  treatise  which  gives  particular 
every   phase  of   papermaking  from   the   saw 
mill  to  the  finishing  room.     (Chemical  cata- 
log Co..  170  Metropolitan  Tower.  New  York. 
$6.) 

A  TEXT  BOOK  OF  PAPERMAKING,  by 

C.    ':  I.   Bevan.      Fifth  edition, 

containing    additional    matter,    and    in    part 

:th  collaboration  of   |.   F.  Briggs. 

(Spon  &  Chamberlain.  120  Liberty  St.,  New 

•k,  $9.) 

THE  ACTION   OF  THE  BEATER,  by   Dr. 
•ml   Smith   (1923).     An  exhaustive  treat- 
ment of  the  subject.      Published   by    British 
Technical  Section.     (Distributed  in  U.  S.  by 
mical  Association  of  the  Pulp  and  Paper 
Industry.  IS  East  41st  St.,  New  York,  $3.60.) 

THE  RECOVERY  AND  MANUFACTURE 
OF  WASTE  PAPER,  by  James  Strachan 

'18).     This  is  a  most  useful  and  sup 
live  work  which  can  be  recommended  to  all 
practical  r>;i  (Spon  X-  Chamber- 

lain,  120  Liberty  St..  New  York.  $4.50.) 

THE  TREATMENT  OF  PAPER  FOR 
SPECIAL  PURPOSES,  by  Louis  Edgar 
Andes  i  1'X)7).  The  processes  of  manufac- 
ture Toducts  are  out- 
lined in  k  of  23'  It  is  ii' 


working  manual,  though  it  contains  a  collec- 
tion of  formulas  And  furnishes  for  parchment 
and  greaseproof  papers,  as  well ,  as  for  a 
whole  series  of  novelty  papers.  (D.  Van 
Nostrand  Co.,  8  Warren  St.,  New  York,  $3.) 

CHEMISTRY     OF     PULP    AND     PAPER 

MAKING,  by  Edwin  Sutermeister  (1920). 
A  practical  book  for  paper  mill  chemists, 
superintendents  and  students.  It  is  based 
on  notes  and  experiences  of  the  author  dur- 
ing a  long  term  of  service  as  chemist  in  the 
industry,  a.->  well  as  study  of  the  literature 
relating  to  the  subject.  It  assumes  a  moder- 
ate knowledge  of  chemistry  on  the  part  of 
the  reader.  (  form  Wiley  &  Sons,  New 
York.  $6.) 

CHEMISTRY     OF     PAPERMAKING,     by 

Griffin  and  Little  (1S94).  This  book  has 
been  out  of  print  for  some  time.  A  photo- 
graphic reproduction  of  it  was  issued  from 
Switzerland  some  time  ago  when  a  copy 
was  procured  from  the  Baker  Company  of 
Cleveland.  Ohio.  (G.  E.  Stechert  &  Co., 
31  East  10th  St.,  New  York,  $8.) 

TECHNICAL  METHODS  OF  ANALYSIS, 

by  Roger  C.  Griffin  (1921).  A  good  work 
for  analytical  chemists.  (McGraw-Hill  Book 

.  370  Seventh  Ave.,  New  York,  $6.) 
THE   PAPER   MILL   CHEMIST,   by   Henry 
Stevens   (1907).     (D.  Van  Nostrand  Co., 
Warren  St.,  New  York,  $4.) 

PAPER  TESTING  METHODS,  by  the  Com- 
mittee on  Paper  Testing,  TAPPI  (revised 
1922).  A  practical  treatise  on  the  analysis 
paper.  (Technical  Association  of  the 
Pulp  and  Paper  Industry,  IS  East  41st  St., 
New  York,  $3.) 

FROM  PAPER  MILL  TO  PRESSROOM, 
by  William  Bond  Wheelwright  (1920). 
(George  Banta  Publishing  Co.,  Menasha, 
Wis.,  $2.) 

PHILLIPS'  PAPER  TRADE  DIRECTORY 
OF  THE  WORLD,  by  S.  Charles  Phillips. 
Usued  yearly.  (S.  Charles  Phillips  &  Co., 
47  Cannon  St.,  E.C.,  London.) 

LOCKWOOD'S  DIRECTORY  OF  THE 
PAPER  AND  ALLIED  TRADES.  Issued 

uially,  in  September.  Contains  a  direc- 
tory of  paper  and  pulp  mills  in  United  States 
and  Canada,  and  classified  lists  of  paper  and 
mill  products,  besides  addresses  of  paper 

i  board  merchants,  twine  manufacturers 
rind  wall  paper  printers.  There  is  also  a 

•ful  reference  list  of  watermarks  and 
brand  names.  (Lockuood  Trade  Journal 
Co.,  10  East  39th  St.,  New  York,  $7.) 


PAPER  TESTING  METHODS 

Microscopical,  Chemical,  and  Physical  Processes 
Described  with  the  Apparatus    Employed 


By 

COMMITTEE  ON  PAPER  TESTING 

ot  the  Technical  Association  of  the 
Pulp  and  Paper  Industry 


Published  by  the 

TECHNICAL  ASSOCIATION  OF  THE  PULP  AND  PAPER  INDUSTRY 

18  East  41st  Street,  New  York  City 
1922 


Copyright,   1922 

by  the 

Technical  Association  of  the  Pulp  and  Paper  Industry 
New  York 


CONTENTS 


Page 

LIST  OF  ILLUSTRATIONS  

6 

I.     PAPER  TESTING    

7 

1  .     Purpose  

7 

2.     Development   

7 

3.     Group    of    Methods  

7 

4.     Record   Cards    

7 

5.     Sampling    

,  7 

6.     Tolerances    

,  7 

7.     Test  Sample  

7 

II.     MISCROSCOPICAL  EXAMINATION   

7 

1.     Estimation  of  Fiber  Content  

7 

a.     Preparation  of  Slide   

•  7 

b.     Discussion  of  Manipulation  

10 

f  .     Common   Stains    

11 

HERZBEHG'S    

11 

JENK'S    

11 

SUTERMEISTER'S    

12 

d.     Special   Stains    

,  12 

LOFTON-MERSITT  SULPHATE  STAIN  

12 

PHLOROGI.UCINOL   

12 

ANILINE  SULPHATE   

•  13 

PARA-NITROANILINE  

13 

THE  C.  G.  BRIGHT  STAIN  

13 

2.     Classification  of  Fibers  Used  in  Papermaking    .... 

13 

3.     Degree  of  Beating  -.  

16 

4.     Specks  or  Dirt  in  Paper   

16 

5.     Starch    

16 

III.     PHYSICAL  TESTING   

17 

1.     Effect  of  Relative  Humidity  

17 

a.     Relative    Humidity    

17 

b.     Moisture     

18 

c.     Weight    

18 

rf.     Bursting  Strength   

18 

e  .     Tearing  Strength   .  .  .  

19 

f.     Folding  Endurance   

19 

g.     Breaking  or  Tensile  Strength  

:  :  19 

2.     Characteristics  of  Paper   .  '.  

19 

a.     Machine  Direction    

19 

b.     Wire  or  Felt   Side  

19 

3.     Area  of  Sample   

19 

4.     Weight  of  Sample   

19 

a.     Balances  and  Scales   

:  20 

/>.     Conversion  Factors   

20 

SUBSTANCE  NUMBER  

20 

METRIC  FACTORS    

20 

ROLL  LENGTHS   

20 

5.     Bursting  Strength    

20 

a.     Description    

20 

b.     Comparison    

20 

c.     Ratio    

20 

6.     Thickness    

21 

a.     Description    

21 

b.     Variations     

...:  21 

7.     Bulk    

21 

S.     Folding  Endurance   

21 

a.     Description    

.'..  21 

535789 


CONTENTS— Continued 


Page 

b.     Calibration    22 

r .     Accuracy    23 

9.     Tensile  or  Breaking  Strength 23 

17.     Description    23 

b.  Wet  Tensile '. . . 24 

r .     Stress-strain    25 

</.     Elongation  at  Rupture  25 

10.  Absorption    25 

a.     Strip  or  Klemm  Method 25 

•b.     Pipette  Method   25 

c .  Total  Absorption : 26 

d.  Blotting  Test  ., .-.- 26 

1 1 .  Opacity  and  Translucency   26 

12.  TeaVing  Test ^ 26 

a.  Knife  Edge  Method  (A.  D.  Little) 27 

b.  Witham  and  Case  Testers 27 

c.  Schopper 27 

d.  Elmendorf 27 

e.  Discussion  of  the  Tearing  Test 27 

13.  Degree  of  Sizing   27 

o.     Flotation  Method 27 

b.  Electrolytic   Method    28 

c .  Stockigt  Method   28 

14.  Finish  or  GloSS   28 

a.  Ingersoll   Glarimeter 28 

b.  Martins-Koenig  Photometer 29 

15.  Volumetric  Composition    29 

16.  Retention  of  Loading 29 

17.  Conducting   Particles    , 30 

18.  Resistance  to  Water  Penetration 30 

IV.  CHEMICAL  ANALYSIS 31 

1.  Ash   Determination    31 

a.  Quantitative    31 

b.  Qualitative  32 

c .  Amount  of  Coating  32 

2.  Paraffin : 32 

3.  Sizing  Materials 33 

a.  Rosin   33 

b.  Glue  and  Casein 33 

c.  Starch 34 

rf .     Dextrine   in   Presence  of   Beater  Starch 35 

4.  Chlorine   35 

5.  Sulphur 35 

6.  Coloring  Matter    36 

7.  Tests  for  Special  Materials , 36 

8.  Free  Acid  in  Paper 36 

9.  Tarnishing  Test   •. . .  36 

V.  INTERPRETATION  OF  DATA : .  37 

1.  Relation  of  Various  Tests  -. 37 

2.  Quality  Indicated  by  Tests  37 

VI.  BIBLIOGRAPHY   (Partial) 38 

1.  Books   38 

2.  Magazine  Articles   38 

INDEX   .  40 


PAPER    TESTING    METHODS 


Annual    Report    of    the    Committee    on    Paper   Testing  Presented   at   the  Annual 

Meeting    of   the   Technical    Association    of    the    Pulp    and 

Paper    Industry,    April    11,    1 922 


Since  the  last  publication  of  the  methods  proposed  by  this 
committee,  there  have  been  a  number  of  methods  and  devices  de- 
veloped for  testing  paper.  There  seems  to  be  a  growing  realization 
that  there  are  not  a  sufficient  number  of  good  methods  or  apparatus 
for  testing  paper.  The  two  notable  instances  of  improvements  will 
K  found  in  the  interest  in  a  sizing  test  and  in  the  tearing  strength 
quality. 

In  view  of  the  above  facts,  it  was  thought  desirable  to  revise  the 
I'aper  Testing  Methods  as  a  whole.  Certain  of  the  data  have  been 
rearranged  to  make  it  more  convenient  and  there  have  been  added 
;t  contents,  list  of  illustrations,  bibliography  and  an  index.  It  is 
believed  that  these  additions  will  make  these  methods  of  consider- 
aMy  greater  value  because  of  their  increased  convenience. 

Minor  changes  have  been  made  in  some  of  the  methods  or 
formula;  and  an  attempt  has  been  made  to  make  the  methods  and 
illustrations  as  up-to-date  as  possible.  In  addition,  a  number  of 
methods  have  been  added  which  will  widen  the  field  of  use  of  the 
I'aper  Testing  Methods.  The  additional  methods  are: 

1.  Sutermeister's    calcium   chloride    stain    for   microscopic    work. 

2.  Lofton-Merrill   slain   for   unbleached  sulphate. 

3.  Relation  between  relative  humidity  and  certain  physical  quali- 
lies  of  paper. 

4.  Methods  'for  determining  the  machine  and  cross  direction  and 
also  the  wire  and  felt  side. 

5.  Factors    for  conversion   to  and   from  the   metric   system   and 
also  for  computing   roll  lengths. 

(>.     Wet  tensile  test. 

7.     Stress-strain    tesl    for    heavy    bag    paper,    indicating    stretch 
under   load. 
X      Additional   melhods   for  absorption. 

9.  Tearing  tesl :  a  brief  discussion  of  live  methods  or  apparatus. 

10.  Conductivity  or   electrolytic   method   for   measuring  the   siz- 
ing quality  of  paper. 

11.  Volumetric  composition  of  paper. 

12.  Method    for   measuring   the   number   of   conducting   particles 
in  thin  paper. 

13.  Resistance  to  water  penetration. 

14.  Sulphur   in  paper. 

15.  Tarnishing  test. 

Throughout  the  report,  wherever  the  author,  inventor  or  origina- 
t'ir  of  a  method  or  apparatus  is  known,  reference  is  made  and 
credit  is  given.  Wherever  data  or  information  are  taken  directly 
from  a  publication,  reference  is  made  to  the  corresponding  number 
<  :  thij  bibliography. 

In  reference  to  the  investigalion  of  microscopic  examination  of 
lilx-rs  and  the  bursting  strength  of  paper,  as  proposed  by  the  com- 
mittee last  year,  it  was  not  possible  to  include  the  results  in  this 
report.  Data  have  been  received  from  about  half  of  the  co-operating 
laboratories,  but  it  is  planned  to  complete  the  study  and  publish  the 
results  later.  The  indications  are,  however,  that  the  various 
laboratories  do  not  get  as  close  check  results  as  would  be  expected. 

It  is  believed  that  the  Paper  Testing  Committee  has  arrived  at  a 
place  where  a  change  of  policy  is  desirable.  In  the  past,  this  com- 
mittee has  suggested  and  proposed  various  methods  of  testing 


which,  in  its  judgment,  were  of  value  in  determining  the  quality  of 
paper.  It  is  thought  desirable  that  TAPPI  authorize  this 
committee  to  investigate  the  following  subjects  with  the  view  to 
putting  paper  testing  on  a  more  scientific  basis.  With  the  active 
co-operation  of  various  laboratories  equipped  for  paper  testing,  it 
is  .believed  that  data  can  quickly  be  collected  to  permit  of  more 
(lelinite  official  methods  of  testing. 

1.  A  survey  be  made  of  the  various  laboratories   with  a   view 
to  determining  the  extent  of  paper  testing  equipment  available. 

2.  The  development  of  standard  official  methods  of  the  Associa- 
tion  to  be  used  by   its  members. 

3.  A  study  of  the  relation  of  the  various  physical  tests  of  paper 
and  an  attempt  made  to  reach  positive  conclusions. 

4.  A  study  of  the  proper  meaning  or  interpretation  of  the  various 
tests  and  an  attempt  to  reduce  the  tests   (chiefly  physical)   to  M>me 
fundamental  units. 

5.  The  determination  of  the  proper  test  for  a  particular  use. 

In  conclusion,  it  is  thought  that  paper  testing  should  be  put  on 
a  firmer  basis  and  that  this  Association  is  responsible  to  the  paper 
industry  for  the  development  of  methods  of  measuring  the  quality 
of  the  paper  and  it  is  hoped  that  this  commitee  will  be  permitted 
to  follow  the  program  suggested  above. 

GEORGE  R.  ATKINSON, 
Scott  Paper  Company, 
Chester,  Pa. 

FREDERICK  A.  CURTIS, 
Paper  Section, 
Bureau   of   Standards, 
Washington,   D.  C. 

CHARLES  A.  POORNESS, 
Kimberly-Clark  Co., 
Neenah,  Wis. 

JOHN  H.  GRAFF,   . 

Brown  Company. 
Berlin,  N.  H. 

HELEN  U.  KIELY, 

American  Writing  Paper  Co., 

Holyoke,   Mass. 

EDWIN    SUTERMEISTER,       . 

S.  D.  Warren  Company, 
Cumberland  Mills,  Me. 

SIDNEY  D.  WELLS, 

Forest  Products  Laboratory, 

Madison,   Wis. 

FREDERICK  C.  CLARK,  Chairman, 
Pejepscot   Paper  Company, 
Brunswick,   Me. 


,        -,    J-    ,»      , 
- 


LIST   OF   ILLUSTRATIONS 


Figure            Title 

Page 

1. 

Chart  of  Paper  Tests  :  

8 

2. 

Test  Record  Card  

9 

3. 

Test  Tube  Shaker  

10 

*4. 

Binocular  Miscroscope  

10 

5. 

Holder  for  Miscroscope  Slide  

12 

6. 

Binocular  Miscroscope   

12 

7. 

Classification  of   Fibers  

13 

8. 

Characteristics  of  Fibers  

14-15 

9. 

Photomicrograph  —  Aspen  

17 

10. 

—  Balsam  Fir   

17 

11. 

—  Chestnut    

17 

12. 

—Hemlock  

17 

13. 

-Rag  Pulp   

18 

14. 

—  Rice  Straw   

18 

IS. 

—  Spruce  Mechanical  Pulp  

18 

16. 

—Tulip  Tree  

18 

17. 

Moisture  Content  of  Paper  

19 

18. 

Quadrant  Scale  

20 

19. 

Torsion  Balance  

20 

20. 

Sheet  Weighing  Device  

21 

21. 

Pea  and  Beam  Scale  

21 

22. 

Mullen  Bursting  Tester  

22 

23. 

Ashcroft  Tester   

22 

24. 

Webb   Tester    

22 

25. 

Thickness  Tester   

23 

26. 

Bulk   Tester    

,  23 

27. 

Folding  Tester    

23 

28. 

Calibrating   Device    

24 

29. 

Green  Folding  Tester  

24 

30. 

Schopper  Tensile  Tester   

24 

31. 

Stress-Strain    Tester    

25 

32. 

Perkins  Tensile  Tester  

25 

33. 

Absorption  Test   

26 

34. 

Relation  ibetween  Filler  and  Blotting  Quality  

26 

35. 

Opacity  Apparatus    

27 

36. 

Witham  Tearing  Tester  

:  .  27 

37. 

Elmendorf  Tearing  Tester   

28 

38. 

Schopper  Tearing  Tester   

28 

39. 

Valley  Size  Tester  

29 

40. 

Sizing  Test   Apparatus    

29 

41. 

Glarimeter    

30 

42. 

Glarimeter    Principle    

30 

43. 

Martins-  Koenig    Photometer    

31 

44. 

Conducting   Particles    

31 

45. 

Rosin   Kxtraction   . 

33 

I'AI'ER     TESTING     METHODS 


PAPER  TESTING  METHODS 

Microscopical,    Physical    and    Chemical    Processes 


I.     PAPER  TESTING 

1.     Purpose 

Tlic  testing  of  paper  is  performed  for  three  reasons  and  it  is 
possible  that  methods  suitable  for  one  purpose  may  not  be  suit- 
able for  another.  These  purposes  are:  (a)  to  study  the  manu- 
facture in  order  to  improve  the  quality,  (b)  to  maintain  a  pre- 
determined quality,  and  (c)  to  determine  whether  the  quality  is 
equal  to  a  predetermined  standard  or  specification.  The  manufac-" 
ttirer  is  interested  chiefly  in  (a)  and  (to),  while  the  user  or  buyer 
is  interested  in  (c),  when  paper  is  bought  on  specification.  It  is 
obvious  that  various  methods  may  be  developed  for  use  in  mills 
that  are  entirely  satisfactory  for  the  development  of  quality  and 
lor  maintaining  that  quality.  •  It  is  thought,  however,  that  the 
methods  used  by  testing  laboratories  in  connection  with  the  pur- 
chase of  paper  on  specifications,  should  be  so  defined  and  stand- 
ardised that  comparable  results  will  be  obtained  by  different  labor- 
atories. The  methods  herewith  given  are  in  some  cases  .merely  tenta- 
tive suggestions  which  can  not  be  accepted  as  standard  without 
further  investigation.  It  must  be  understood,  however,  that  in  de- 
termining what  tests  to  make,  that  the  purpose  for  which  the  paper 
is  to  be  used  is  of  primary  importance,  and  that  that  test  should 
•K  used  which  will  indicate  the  quality  that  is  specifically  desired. 

2.     Development 

I'aper  testing  has  developed  rather  slowly  in  this  country  and 
many  of  the  methods  are  of  foreign  extraction,  as  are  some  of 
the  instruments  and  apparatus.  However,  a  considerable  amount 
of  development  has_  taken  place,  and  there  are  a  greater  number 
of  methods  now  available.  This  development  has  not,  however, 
been  in  any  systematic  manner  and  has  been  spread  over  the  whole 
field  of  testing,  to  meet  special  conditions.  A  systematic  study 
should  be  made  and  standard  methods  developed  and  used. 

3.     Groups   of   Methods 

For  convenience,  the  various  methods  of  testing  are  grouped 
into  three  classes: — microscopical,  physical  and  chemical.  In  most 
cases,  some  of  the  methods  from  each  class  are  necessary.  The 
accompanying  chart  ( P'ig.  1 )  indicates  some  of  the  tests  given  and 
shows  the  relation  between  them.  It  is  obvious  that  all  the  tests 
indicated  are  not  necessary  in  any  one  particular  case  but  such 
tests  should  be  used  that  will  indicate  the  quality  of  paper  necessary 
for  a  particular  purpose. 

4.     Record  Cards 

Complete  laboratory  records  should  -be  kept  of  all  tests  (especially 
original  data)  and  in  such  a  manner  as  to  be  always  available. 
The  accompanying  5  by  8  in.  record  with  both  sides  reproduced  is 
offered  as  a  suggestion.  (Fig.  2)  though  individual  requirements 
may  necessitate  certain  alterations. 

5.     Sampling 

The  proper  sampling  of  paper  for  test  or  the  interpretation  of 
the  test  data  in  connection  with  sampling  has  been  neglected.  It 
is  pointed  out,  however,  that  no  test  data  is  more  accurate  than 
the  sampling.  This  applies  with  especial  force  in  connection  with 
the  testing  of  a  shipment  of  paper  to  determine  whether  it  con- 
forms to  a  definite  specification.  It  is  oSvious  that  cases,  bundles. 


frames,  rolls,  etc.,  must  be  sampled  differently  but  as  much  care 
should  be  exercised  in  this  connection  as  in  the  sampling  of  wood 
gulp_for  moisture. 

6.     Tolerances 

The  va'.ue  of  the  test  data  is  accurate  only  when  a  large  number 
of  tests  are  made  or  when  proper  tolerance  is  allowed  for.  This 
tolerance  is  necessary,  owing  to  the  errors  which  are  inherent  in  the 
whole  process  of  paper  testing.  The  errors  are  introduced  (a)  'by 
improper  or  incomplete  sampling,  (b)  by  the  natural  lack  of  uni- 
formity in  paper,  due  to  its  structure,  and  (c)  by  the  error  of  the: 
apparatus  or  method  of  testing  which  may  either  be  inherent  in  the 
apparatus  or  due  to  improper  manipulation. 

7.    Test  Sample 

•The  original  sample,  obtained  by  .proper  sampling,  should  be  suf- 
ficiently large  and  of  enough  sheets  to  enable  all  the  proposed  tests 
to  be  made  without  recourse  to  an  additional  sample.  The  various 
tests  should  lie  made  on  the  several  sheets  of  the  sample  in  order 
to  obtain  a  reasonably  fair  average. 

II.     MICROSCOPICAL   EXAMINATION 
1.     Estimation  of  Fiber  Content 

a.  f'n-farutiiiii  of  Slide.—  Secure  a  representative  sample  by 
clipping  a  piece  of  about  the  area  of  a  cent  from  the  corners  of 
several  of  the  sheets  to  be  tested.  Place  the  samples  in  a  dish. 
small  beaker,  or  test  tube,  cover  with  a  0.5  per  cent  caustic  soda 
solution  and  bring  to  a  boil  to  remove  sizing  or  other  binding 
material.  The  pieces  are  next  drained,  washed  several  times  in 
tap  water,  rolled  into  a  small  pill  or  ball  between  the  thumb  and 
first  finger  for  about  1  min..  then  placed  in  a  test  tul>e,  about 
half  filled  with  water  and  shaken  vigorously,  so  as  to  defiber 
thoroughly  the  particles  of  paper.  A  small  part  of  this  deftbered 
mass  is  removed  from  the  test,  tube  by  the  aid  of  a  microscopic 
needle  (Note  1)  thoroughly  dried  on  absorbent  paper  (Note  2) 
that  is  free  from  lint,  placed  on  a  microscopic  slide  and  covered 
with  several  drops  of  Herzberg's  stain.  The  fibers  are  carefully 
pulled  apart,  by  the  aid  of  microscopic  needles,  so  that  they  'will 
not  lie  too  much  in  a  bunch  and  are  then  covered  with  the  cover 
glass.  (Note  3.)  The  slide  is  now  ready  for  an  estimation  by 
the  aid  of  the  microscope. 

It  is  suggested  that  after  the  small  sample  of  paper  has  been 
boiled  with  0.5  per  cent  caustic  soda,  that  the  sample  be  next 
washed  with  0.5  per  cent  hydrochloric  acid  and  finally  with  water. 
It  is  difficult  to  wash  all  the  caustic  from  the  fibers  and  an  addition 
of  hydrochloric  acid  seems  advisable. 


ee 

First  method.  Use  a  lest  tube  of  about  ^-in.  diameter  and  about  6  in  long 
keep  the  fibers  diluted  with  water,  FO  that  they  will  mix  readily  when  shaken 
vigorously.  The  fibers  mix  very  easily  if  the  test  tube  is  about  two-thirds  full 
]?at"J"yj  5b-ers'  The  micros<:°P'c  needle  referred  to  is  a  pointed  steel 
needle  imbedded  in  a  small  wood  or  metal  handle.  Shake  test  tube  and  then 
quickly  incline  it  at  a  sharp  angle.  Insert  the  point  of  the  microscopic  needle 
and  remove  a  small  bundle  of  fibers  for  use  in  making  up  the  microscopic 
slide.  The  foregoing  method  of  procedure  is  best  where  the  fibers  are  long, 
such  as  in  a  rag  bond,  ledger,  or  writing  paper,  also  for  long-fibered  wood 
papers  made  of  new  s'llphite  cc  sulphate  pulps.  For  groundwood  papers  or 
where  the  fibers  are  very  sh.,it  anil  contain  a  large  quantity  of  fine  broken 
particles  such  as  Cooked  old  iraper  stock,  the  use  of  the  needle  to  secure  a 
representative  sample  will  result  in  securing  more  long  fibers  than  short  fibers 
with  a  result  of  inaccuracy.  For  papers  containing  much  short  fine  fiber  it  is 


. 
l>est  to  use   the  second   methid. 


PAPER    TESTING     METHODS 


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FIG.  1.    CHART  OF  PAPER  TESTS 


PAPER    TESTING    METHODS 


Serial  No.      £?<?£ 

FROM 
The  Paper-  Comf>a/iy  o/  Amer/ca. 

Received       3-/S-ZZ 

Folder  No.    33(333 

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MARKED 


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Weight  (25x40,  500)= 65    Ibs. 

Weight  (  /7*2*  '  600               )=     .    .  24.3     Ibs. 

Bursting  strength 4/      points 

Thickness= inches 

Ratio  bursting  strength  to  wt.  (25  x  40,  500) 


FIBER 
COM- 
POSITION 


CHEMICAL 
TESTS 


R«g 

Chemical  pulp 

Chemical  pulp,  bleached    .    . 
Chemical  pulp,  unbleached    . 

Coniferous  fiber 

Broad-leaf  fiber 

Ground-wood  pulp    .... 
Manila  and  jute 


so 


Jo 


Ash AS     % 

Total  resins fo 

Animal  size Present    % 


SPECIAL  PHYSICAL  TESTS 


Double  folds  (Schopper) 

Tearing  strength 

Breaking  strength    .  Qry  ..... 

Elongation  tinder  load  of Ibs. 

Breaking  length 


Machine 
Direction 


76Z 
69 


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Direction 


63 
63 

6020 


Numb. 


yds. 


Weight  data 


64.25 


—       65 


'0.98Y.  /O    x  9 


REMARKS: 


WeTBrvafanq  Strength 

Correct/ofi  formvfa.      y* 


No. 


BURSTING 

STRENGTH 

(Points) 


Crost. 


THICKNESS 
(Inches) 


BREAKING  STRENGTH 


Machine 
Direction 


Cross 
Direction 


TEARING  STRENGTH 


Machine 
Direction 


Cross 
Direction 


FOLDING  ENDURANCE 
(No.  ol  Double  Folds) 


(Strip  15  mm  wide) 


Machine 
Direction 


Cross 
Direction 


1 
2 
3 
4 
5 
6 
7 
8 
9 
10^ 

Mean 


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NO. 


ABSORPTION  IN  10  MINUTES 
Klemm  Method 


Machine  Direction      Cross  Direction 


Breaking  strength  in  Ibs.  per  1"  width-tBreaking  strength  in  kg  per  15  mm  width)x(3.73). 

Breaking  length  in  yards=<  Breaking  strength  inlbs.  per  1"  width)x(13,889)+(Wt»  in  Ibs.  per  25X<0,  500). 

Wt.,  in  Ibs.,  el  ream  oI5()Osheets-(Wt.  of  1  sheet  in  grams)x(U02) 

Wt.  in  grams  per  sq.  meter=(Wt.  in  Ibs.  per  25X40,  500)  x  (1.406). 

Wt.  in  grams  per  sq.  meter  —  (Wt.  in  Ibs.  of  any  ream  o'500sheets)X(140G.13)-f-(Area  of  sheet  in  sq.  in.). 

Wt.  of  any  500-sheet  ream—  (Wt.  in  grains  per  sq.  meter.  X(Area  ol  sheet  in  sq.  in.)+(140<U3). 


NOTE 


Bursting  strength  _______  .............. 


Breaklnj  strength 
Tearing  strength 
Folding  endurance  _____ 


NAME  OR  NO. 


...M*t//ea. 


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UNIT 


INITIAL 


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,    FIG.  2.     TEST  RECORD  CARD 


10 


PAPER     TESTING     METHODS 


Second  method*(37).  In  using  this  second  method  it  is  advisable  to  have 
the  fibers  slightly  more  dilute  in  the  test  tube,  than  is  the  case  in  the  first 
method,  also  the  test  tubes  should  be  about  three-quarters  of  an  inch  in  diam- 
eter by  about  8  in.  long.  In  place  of  the  microscope  needle  a  10-in.  glass  tube 
<  f  abcut  seven  thirty-seconds  of  an  inch  in  diameter  is  employed.  This  glass 
lrl>c  has  one  end  rounded  so  as  not  to  have  sharp  edges  and  the  other  end  is 
p:  ovided  with  a  small  rubber  bulb.  This  serves  as  a  dropper.  Spence  and 
Kranss  describe  the  modus  operandi  as  follows:  "When  ready  to  prepare  the 
slides,  the  test  tube  is  well  shaken,  the  dropper  inserted,  with  as  little  delay 
as  possible,  two  inches  below  the  surface,  two  bubbles  of  air  expelled  and  a 
little  less  than  half  an  inch  of  the  mixture  drawn  into  the  tube.  This  is  trans- 
ferred to  slides,  completely  emptying  the  dropping  tube,  which  will  make  four 
drops.  The  slides  are  placed  in  an  air  bath  to  expel  moisture,  cooled,  and  each 
drop  stained  with  Herzberg  stain,  just  before  it  is  to  be  examined.  The  excess 
stain  is  then  removed — after  the  colors  have  developed  to  a  maximum  point, 
about  3  min.  required — by  tilting  the  slide  and  the  cover  glass  placed  over 
the  spot."  After  the  cover  glass  is  in  place,  it  should  be  pressed  down  gently 
to  expel  excess  stain  and  any  excess  stairj  removed  by  absorbing  it  with  a  piece 
of  blotting  or  filter  paper. 

Note  2 — The  absorbent  paper  used  should  have  a  hard,  smooth  surface  so 
that  no  lint  will  adhere  to  the  sample  of  fibers.  As  soon  as  the  sample  is  dry 
it  may  be  removed  to  the  miscroscopic  slide  and  is  then  ready  for  the  drop  of 
stain.  A  second  method  of  drying  the  sample  is  to  put  it  on  the  microscope 
slide  and  then  touch  it  with  the  corner  of  a  piece  of  folded  filter  paper  of 
ordinary  quality.  For  this  purpose;  a  cheap  grade  of  filter  paper  may  be  cut 
into  pieces  about  1 J4  by  4  inches.  This  makes  a  handy  size  for  use  in  drying 
the  sample  and  also  in  removing  the  excess  stain  frrm  around  the  edges  of  the 


eter.  The  round  or  square  cover  glasses  are  necessary  for  high  magnification 
and  have  one  disadvantage  in  that  they  are  very  fragile.  The  third  type  of 
cover  glass  is  the  same  size  as  the  microscope  slide,  and  if  thin  microscope 
slides  are  used  then  a  second  microscope  slide  may  be  used  as  the  cover  for 
the  first.  The  chief  advantage  of  the  large  cover  glass  is  that  it  permits  three 
or  four  fields  to  be  made  up  one  each  slide. 


FIG.  3.    TEST  TUBE  SHAKER 

BY  M.   B.  SHAW,   BUREAU  OF  STANDARDS 


cover  glass.  Care  must  always  be  exercised  to  prevent  the  sample  uf  fibers 
to  be  tested  from  becoming  contaminated  with  fibers  from  the  absorlient  paper 
or  filter  paper.  A  third  method  of  drying  the  sample  of  fibers  is  to  place  them 
•  on  a  microscope  slide  and  evaporate  the  moisture  in  a  current  of  heated  air, 
in  an  oven  or  by  some  other  suitable  arrangement. 

In  regard  to  drying  the  small  sample  of  the  fibers  on  the  microscope  slide, 
attention  is  called  to  the  fact  that  the  sample  must  be  dried  so  that  the  stain 
will  not  be  diluted  and  yet  must  not  be  dried  too  hard  because  then  it  is 
difficult  to  separate  the  fibers  and  the  staining  does  not  take  place  uniformly. 

Note  3 — There  are  three  kinds  of  cover  glasses.  The  first  two  are  very  thin 
pieces  of  glass  either  round  or  square  of  approximately  half  an  inch  in  diam- 


b.   Discussion  of  Manipulation.—  T\\e  following   suggestions   are 
offered  to  those  just  beginning  these  tests: 

It  is  absolutely  essential  to  'have  a  satisfactory  stain  or  else  the 


Fir,.  4.     BiNccur.AR  MICROSCOPE 

results  will  be  worthless.  To  test  out  a  stain  make  up  a  mixture 
of  about  equal  parts  of  bleached  soda  pulp,  bleached  sulphite  pulp 
and  rag  filter  paper.  Prepare  a  microscope  slide  from  this  mixture 
and  stain  with  the  stain  to  be  tested.  If  the  stain  is  correct,  then 
the  soda  pulp  should  show  a  dark  blue  color,  due  to  the  thicker  and 
more  opaque  fiber  walls,  the  sulphite  pulp  should  show  a  //.tr/i/  />/!«•. 
due  to  the  thin  filler  walls  and  the  rag  fibers  will  show  a  red  or 
tame-red  color.  If  the  blue  color  is  more  of  a  violet,  then  too  much 
iodine  is  present  and  more  water  or  xinc  chloride  should  be  added. 
Zinc  chloride  produces  'the  'blue  color,  iodine  produces  the  red  and 
the  yellow  colors  and  the  addition  of  water  serves  to  weaken  the 
color  that  predominates. 

In  some  cases  where  it  is  necessary  to  examine  all  grades  of 
paper,  it  is  advisable  to  keep  several  stains  on  hand.  A  stain  that 
gives  the  best  color  on  groundwood  and  bleached  sulphite  seldom 
gives  a  correct  color  on  mixtures  of  rag,  bleached  sulphite  and 
soda  pulps.  In  such  a  case,  make  up  one  stain  so  that  it  will 
give  a  bright  Iciinni  yellow  on  a  known  sample  of  groundwood 
pulp  and  a  slightly  greenish  blue  on  unbleached  sulphite.  For  the 
mixture  of  rag,  bleached  sulphite  and  soda  pulp,  so  adjust  a  second 
stain  that  the  rag  shows  as  a  clear  trine-red,  the  sulphite  as  a  blue 
and  the  soda  fibers  as  a  dark-  blue.  In  testing  out  a  stain  always 
have  on  hand  authentic  samples  of  pulp  so  these  mixtures  may  be 
made  up. 

To  check  estimates  of  fiber  analysis,  slides  of  fibers  in  known 
proportions  are  made.  Pure  stock  is  l>eaten  in  a  small  ibeater 
and  made  into  hand  sheets.  Sheets  of  the  various  pure  fibers 
are  kept  under  the  same  atmospheric  conditions.  To  make  up  a 
field  of  known  composition  take  weights  of  the  pure  fiber  sheets 
and  make  up  a  total  of  at  least  5  g.  in  proportions  to  give 
the  percentage  desired.  Disintegrate  and  mix  thoroughly  by  shak- 
ing with  shot  in  a  bottle  or  by  the  action  of  a  small  disintegrator. 


PAPER    TESTING    METHODS 


11 


Sample  and  make  up  the  slide  as  for  any  disintegrated  paper 
sample. 

The  estimation  of  the  fiber  content  is  based  on  the  relative  pro- 
portion of  the  kinds  of  fibers  contained  therein,  expressed  on  the 
percentage  'basis,  considering  the  total  fiber  content  as  100  per  cent. 
In  making  a  fiber  estimation  no  account  is  taken  of  the  per  cent 
of  clay,  alum,  size,  etc.,  that  may  be  contained  in  the  paper.  It  is 
always  advisable  to  make  up  at  least  two  separate  samples  of  fiber 
taken  from  the  test  tube  and  the  final  result  should  !be  the  means  of 
all  observations  on  these  two  separate  slides.  In  special  cases  it 
may  be  necessary  to  make  up  four  separate  fields. 

'There  are  two  methods  of  making  the  determination  for  fiber  con- 
tent. One  is  the  count  method,  the  other  is  the  estimation  method. 
Both  methods  have  their  advocates  and  both  give  good  results. 
This  committee,  however,  recommends  the  estimation  method,  be- 
lieving it  to  have  the  following  advantages : 

(1)  It  is  more  accurate  under  certain  conditions,  namely,  in 
making  groundwood  determinations,  and  of  equal  accuracy  under 
all  other  conditions;  (2)  it  is  much  quicker;  (3)  it  is  easier  to 
teach  an  individual  to  estimate  correctly  than  to  count  correctly; 
(4)  it  is  possible  to  make  up  standard  mixtures  for  ready  com- 
parison. 

The  estimation  method  involves  training  the  eye  by  the  com- 
parison of  unknown  samples  with  standard  mixtures  of  known 
composition.  The  result  of  each  observation  on  each  part  of  a 
field  examined,  should  be  written  down  and  the  mean  of.  all  the 
observations  is  the  result  to  be  reported  as  final.  Accuracy  in 
the  estimation  method  involves  practice  and  continual  reference  to 
known  standards.  Unstained  slides  of  these  standard  mixtures 
should  be  kept  handy  to  be  made  up  in  case  there  is  any  doubt 
a:bout  the  sample  being  tested. 

There  is  a  third  method  for  fiber  determination  that  has  been 
proposed  by  Spence  and  Krauss  *(37)  which  is  worthy  of  descrip- 
tion here  and  recommendation  to  the  Technical  Association.  This 
is  known  as  the  fiber-weight-length  method.  The  procedure  is  as 
follows:  Samples  are  made  up  as  described  under  Note  1,  second 
method.  The  slide  is  placed  under  a  microscope  of  160  diameters 
and  the  lengths  of  the  various  fibers  are  measured  in  terms  of  the 
diameter  of  the  field  seen  through  the  microscope.  An  adjustable 
stage  is  also  essential  as  otherwise  it  would  not  be  possible  to  move 
systematically  over  the  entire  sample  to  be  examined.  After  four 
samples  have  been  estimated  as  above  described,  the  figures  are 
added  together  to  get  the  total  length  of  each  kind  of  fiber  present. 
The  total  length  of  each  kind  of  fiber  present  multiplied  each  by 
its  own  weight  factor  gives  a  set  of  results  that  are  directly  com- 
parable and  may  "be  converted  into  the  per  cent  of  each  kind  of 
fiber  present.  The  weight  factors  as  determined  'by  Spence  and 
Krauss  are  as  follows:  Rag,  1.000;  hemlock  pulp,  0.870;  poplar 
pulp.  0.454;  birch  pulp,  0.6S2;  beech  pulp,  0.525 ;  maple,  0.365. 
This  method,  which  is  undoubtedly  a  step  in  the  right  direction,  is 
recommended  as  a  method  to  be  used  in  cases  of  dispute  'between 
two  different  analyses.  It  is  a  very  slow  method  and  cannot  there- 
fore be  used  where  many  routine  samples  must  be  examined  each 
day.  The  Spence-Krauss  method  is  undoubtedly  the  only  method 
that  will  enable  a  determination  of  the  proportion  of  the  various 
kinds  of  wood  present,  such  as  a  mixture  of  hemlock,  beech,  poplar, 
birch,  maple,  etc. 

In   any   method  of   testing   it   is   always    advisable   to    make   use 

No  definite  recommendation  is  given  in  regard  to  the  microscope  magnifica- 
tion. This  must  be  left  to  the  individual  preference.  Satisfactory  estimations 
may  be  made  with  a  magnification  as  low  as  45  diameters  and  equally  satis- 
factory work  is  being  done  with  magnifications  as  high  as  120.  The  lower 
magnification  has  the  advantage  of  giving  larger  fields,  whereas  the  higher 
magnification  gives  more  of  the  detail  of  the  markings  of  a  fiber.  The  mo- 
nocular and  binccular  microscopes  both  have  their  advocates,  and  like  the  mag- 
nifying power,  it  is  very  largely  a  matter  of  getting  used  to  a  certain  procedure. 
Where  only  one  microscope  can  be  purchased  it  is  better  to  use  a  monocular,  as 
it  can  be  fitted  with  more  attachments  to  suit  special  needs.  It  may  be  well 
to  add  that  a  low  power  of  about  25  diameters  for  examining  specks  and  sur- 
faces, also  a  high  ]>ower  of  350  or  400  for  details  of  fiber  markings  will  often 
be  found  to  be  of  use.  Spence  and  Krauss*(37)  recommend  a  magnification 
of  160  diameters. 


of  all  possible  apparatus  that  may  be  of  assistance  in  carrying 
out  the  method  described.  There  are  no  holders  for  microscope 
slides  on  the  market,  therefore  a  brief  description  will  be  given 
and  it  may  be  constructed  at  almost  no  expense  for  labor  or 
material. 

The  holder  for  the  microscope  slides  is  made  as  follows : 
Take  two  pieces  of  brass  34-  in.  thick  by  y^  in.  wide  by  3  in.  long 
(oak  or  maple  may  be  used  if  the  brass  is  not  obtainable),  then 
cut  a  groove  }^  in.  wide  by  V&  in.  deep  along  one  of  the  longitudinal 
edges  of  the  brass  strip.  This  groove  then  serves  as  a  rest  for  the 
glass  slides. 

The  pins  (see  Fig..  5)  serve  to  prevent  the  glass  slide  from  slip- 
ping out  of  the  grooves  while  the  bundles  of  fibers  are  being  teased 
apart.  Also  note  the  parts  on  the  sketch  marked  "Painted  black" 
and  '"White  surface."  These  serve  as  a  background.  The  glass 
slide  is  placed  over  the  black  'background  when  the  unstained  fibers 
are  first  put  on  the  glass  slide,  as  the  light  (almost  white)  colored 
fibers  show  up  best  with  a  black  background.  After  the  Herzberg 
stain  is  added,  the  glass  slide  is  pushed  to  the  other  end  of  the 
brass  holder,  which  brings  it  over  the  white  background  and  causes 
the  dark-stained  fibers  to  show  up  more  distinctly  and  enables  even 
the  smallest  bundles  to  be  separated. 

For  best  results  for  microscopic  work,  a  clear  north  light  is  de- 
sirable, and  is  to  be  preferred.  However,  where  there  is  a  large 
amount  of  routine  testing  that  must  be  done,  it  is  more  advisable 
to  have  a  more  constant  source  of  light.  There  are  various  types 
of  lamps  available  but  good  results  can  be  obtained  with  a  Mazda 
nitrogen-filled  lamp  of  150  watts.  It  is  necessary,  however,  to  use 
a  blue  "daylight"  filter  in  that  cas'e.  It  is  to  be  noted  that  the  color 
of  the  stained  fibers  on  the  slide  will  be  somewhat  different  for  the 
two  kinds  of  illumination. 

c.     Common  Stains. 

HERZBERG'S.  *(10). — The  Herzberg  stain  is  made  according  to 
the  following  formula : 

Solution  A — 2O  g.  zinc  chloride. 

10  cc.  of  water   (preferably  distilled). 
Solution  B — 2.1  g.  potassium  iodide. 

0.1   g.   iodine  crystals. 

5.0  cc.  of  water   (preferably  distilled). 

Dissolve  solutions  A  and  B  separately,  then  mix  and  allow  to 
stand  several  hours,  or  until  all  sediment  has  settled  out.  The 
clear  liquid  is  next  decanted  and  is  ready  to  'be  used  in  staining  the 
fibers.  All  iodine  solutions  must  be  kept  in  the  dark,  as  otherwise 
they  deteriorate  rapidly.  The  Herzberg  stain  is  a  selective  stain, 
that  is,  it  has  selective  staining  properties.  Ground  or  mechanical 
wood  pulp,  jute,  flax  tow,  uncooked  manila  hemp  and  in  fact  most 
every  vegetable  fibrous  material  containing  large  quantities  of  ligno- 
cellulose,  is  colored  yellow  or  lemon  yellow.  The  removal  of  their 
lignocellulose  content  changes  the  staining  effect  from  a  yellow  to  a 
blue  or.  wine-red  color,  though  jute  and  a  few  other  fibers  remain 
unchanged  in  color.  Thoroughly  cooked  and  bleached  soda  and 
sulphite  pulps,  cooked  and  bleached  straw  pulp  and  esparto  are 
colored  blue  or  navy  blue.  'Cotton  and  linen  rags,  thoroughly 
cooked  and  bleached  manila  hemp,  and  certain  of  the  Japanese 
fibers  are  colored  a  wine  red. 

In  connection  with  the  Herziberg  stain,  the  following  alternative 
formula  is  suggested:  25  cc.  zinc  chloride  solution  (saturated) 
at  70°  F. ;  5.25  g.  potassium  iodide;  0.25  g.  of  iodine,  and  12.5  cc. 
water.  Owing  to  the  difficulty  of  obtaining  zinc  chloride  of  uniform 
moisture  content,  it  has  'been  found  more  satisfactory  to  use  a 
saturated  zinc  chloride  solution.  By  mixing  the  ingredients  as 
stated  above,  the  proper  stain  can  'be  obtained  at  once. 

JENK'S. — The  stain  known  as  "Jenk's  Stain"  is  of  value  when 
it  is  desired  to  ascertain  definitely  small  amounts  of  rag  fiber 
with  only  a  poor  Herzberg  stain  available :  To  50  cc.  of  saturated 
magnesium  chloride  solution  add  2l/2  cc.  of  iodine  potassium  iodide 


12 


PAPER    TESTING    METHODS 


solution  made  up  as  follows:  Potassium  iodide,  2  g. ;  iodine,  1:15 
g.,  and  water,  20  cc.  Use  exact  quantities  and  keep  solutions  from 
the  light;  the  stain  is  kept  best  in  a  small  brown  bottle  with  a 
pipette.  Rag  fiber  is  stained  brown,  straw  is  stained  blue-violet, 
groundwood  is  stained  yellow,  and  chemical  wood  either  no  color  or 
deep  red. 

SUTERMEISTER'S.  *(3). — A  stain  which  is  considered  by  some  to 
be  better  than  the  Herrberg  stain  is  made  up  as  follows : 

Solution  A. — 1.3  g.  iodine  and   1.8  g.  potassium  iodide  in  100  cc.  of  water. 
Solution  B. — A  clear,  practically  saturated  solution  of  calcium  chloride. 

In  using  this  stain  apply  a  drop  or  two  of  Solution  A  to  the 
moist  fibers  on  the  microscope  slide.  After  a  minute  or  so  remove 
the  stain  by  means  of  a  blotter  and  immediately  put  on  a  drop  or 
two  of  Solution  B.  Pull  the  fibers  apart  and  distribute  them  by 
means  of  needles  as  'before  and  drop  on  a  cover  class  or  thin 
miscroscope  slide.  Any  excess  of  Solution  B  should  'be  removed  by 
absorbing  it  with  moist  blotting  paper.  This  stain  is  also  selective 
in  its  action,  the  colors  produced  being  as  follows : 

Red  or  brownish  red :  cotton,  linen,  hemp,  ramie. 

Dark  blue:  bleached  soda  pulps  from  deciduous  woods. 

Bluish  or  reddish  violet :  bleached  sulphite  fibers  and  the  thor- 
oughly cooked  part  of  the  unbleached  sulphite. 

Greenish  :  jute,  manila  and  the  more  lignified  fibers  in  unbleached 
sulphite. 

Yellow,  groundwood. 

As  with  the  Herzberg  stain  this  one  should  be  adjusted  by  trial 
on  known  mixtures  of  fiber  until  it  shows  satisfactory  difference  in 
color.  The  two  solutions  should  be  protected  against  evaporation 


s 


FIG.  5.    HOLDER  FOR  MICROSCOPE  SLIDE. 

and  dust  but  light  does  not  change  their  staining  properties  to  any 
extent. 

d.    Special  Stains. 

There  are  many  stains  in  use  for  special  purposes  and  a  descrip- 
tion of  them  is  therefore  advisable. 

LOFTON-MERRITT  SULPHATE  STAIN.  *(99). — The  stain  which  was 
found  to  be  most  satisfactory  in  differentiating  between  unbleached 
sulphite  and  sulphate  pulps  or  fibers  was  a  mixture  of  one  part 
of  a  2  per  cent  aqueous  solution  of  malachite  green  and  two  parts 
of  a  1  per  cent  aqueous  solution  of  basic  fuchsine,  or  magenta. 
The  solutions  were  made  up  according  to  the  following  formulas, 


kept   in  tightly   stoppered   separate   bottles,   and   mixed  only    when 
wanted  for  use: 

A — Malachite  green    2  g. 

Distilled   water    100  cc . 

B — Basic  f uchsina  1  g. 

Distilled  water   1 00  cc . 

Since  there  is  considerable  variation  in  the  quality  of  dyes 
from  various  sources,  it  is  not  to  be  expected  that  any  given 
combination  of  dyes  or  method  of  procedure  will  best  fit  all  cases ; 
it  is,  indeed,  more  than  probable  that  the  compound  stain  will 
have  to  be  modified  somewhat  as  to  its  two  components,  depending 
on  the  source  of  the  dyes. 


FIG.  6.    BINOCULAR  MICROSCOPE 

After  this  stain,  therefore,  has  been  made  up  according  to 
formula,  it  will  be  necessary  to  test  it  out  on  samples  of  sulphite 
and  sulphate  fibers.  To  do  this,  samples  of  unbleached  sulphite 
and  sulphate  pulps  should  be  prepared  and  a  few  fibers  of  each 
placed  on  a  slide,  care  being  taken  not  to  get  the  two  samples  mixed. 
The  fibers  are  then  dried  and  stained,  as  directed  below,  and  then 
examined  under  the  microscope.  All  the  sulphate  fibers  should 
have  a  blue  or  Wm--.^''<'<'/i  color,  and  all  the  sulphite  fibers  sin  mid 
have  a  (>urple  or  laicndcr  color.  If  any  purple  fillers  appear  in  the 
sulphate  pulp  this  indicates  that  too  much  fuchsine  is  present  in  the 
combination,  and  a  little  more  malachite  green  solution  must  be 
idded  to  counteract  this  effect.  If,  on  the  other  hand,  some  of  the 
sulphite  fibers  show  green  or  blue,  there  is  too  much  malachite 
i;reen  in  the  combination,  and  more  fuchsine  solution  must  be  added. 
Of  course  the  analyst  must  be  sure  that  he  is  using  authentic  samples 
of  the  two  pulps  for  this  test.  When  tested  out  in  this  manner 
and  the  proper  combination  found,  the  stair  is  ready  to  be  used 
on  unknown  combinations  of  fibers  containing  either  unbleached 
sulphite  or  sulphate,  or  'both. 

A  mixture  of  one-half  sulphite  and  one-half  sulphate  may  also 
be  used  to  test  out  the  stain,  the  proper  combination  for  the  stain 
being  indicated  when  one-half  of  the  fibers  are  colored  blue,  and 
the  other  half  purple. 

The  stain  should  not  be  used  for  more  than  a  few  hours  after 
being  compounded  and  should  be  made  up  anew  at  least  each  day. 

PHLOROGLUCINOL. — Dissolve  5  g.  of  phloroglucinol  in  a  mixture 
of  125  cc.  of  distilled  water  and  125  cc.  of  concentrated  hydro- 
chloric acid.  The  solution  should  be  kept  in  the  dark  as  much 
as  possible  as  it  is  prone  to  lose  its  staining  property  on  exposure 
to  light.  This  solution  produces  a  inagrnla  or  wine-red  color  on 


PAPER    TESTING    METHODS 


13 


mechanical  pulp.  The  color  may  easily  be  noted  by  applying  some 
of  the  stain  to  a  piece  of  news  print  paper.  There  is  approximately 
80  per  cent  of  mechanical  pulp  in  newspaper  so  that  a  deep  magenta 
color  is  developed.  The  depth  of  color  is  an  indication  of  the 
amount  of  mechanical '  pulp  present.  A  very  light  shade  of  color, 
however,  does  not  necessarily  prove  the  presence  of  mechanical 
pulp,  as  partly  cooked  jute,  partly  cooked  unbleached  sulphite  pulp, 
and  some  other  fibers  are  also  slightly  colored. 

An  additional  formula  is  as  follows : 

Phloroglucine     2  g. 

Alcohol  (95%)    100  cc. 

Cone.  HC1 50  cc. 

ANILINE  SULPHATE. — Dissolve  5  g.  of  aniline  sulphate  in  50  cc. 
of  distilled  water  and  acidulate  with  one  drop  of  concentrated 
sulphuric  acid.  This  stain  produces  a  yeltov.1  color  on  papers  con- 
taining a  large  percentage  of  mechanical  pulp.  This  stain  is  not 
quite  as  sensitive  to  mechanical  pulp  as  phloroglucinol,  but  it  is 
easier  to  obtain  and  prepare. 

PARA-NITRCANJLINK. — Saturated  solution  in  concentrated  hydro- 
chloric acid.  This  stain  produces  an  orange  yellow  color  in  the 
presence  of  mechanical  pulp  and  other  lignified  fibers. 

.THE  C.  G.  BRIGHT  STAIN.  *(78). — This  is  used  for  distinguish- 
ing between  bleached  and  unbleached  pulps. 

Solution  A:  Ferric  chloride  solution  (n/10  normal)  equal  to  2.7  g. 
FeCl36H2O  per  100  cc.  distilled  water. 

Solution  B:  Potassium  ferricyanide  solution  (n/10  normal)  equal  to  3.29  g. 
K3Fe  (CN)0  per  100  cc.  distilled  water. 

Solutions  A  and  B  should  each  be  filtered  through  a  fresh  filter  into  clear 
glass  stoppered  bottles.  Equal  volumes  are  mixed  fresh  whenever  the  reagent 
is  used. 

Solution  C:  Substantive  red — o.4  g.  of  benzopurpurin  4B  extra  (Bayer 
Co.),  0.1  g.  of  oxamine  brilliant  red  BX  (Badische  Co.)  and  100  cc.  of  dis- 
tilled water.  Have  water  hot  and  stir  in  the  dyes  slowly. 

The  staining  solutions  are  used  in  tall  narrow  cylindrical  beakers 
which  are  set  into  a  water  'bath.  The  slides  are  suspended  in 
the  beaker  by  a  clamp  which  holds  them  at  their  upper  ends,  the 
clamps  resting  across  the  top  of  the  beakers.  The  bath  is  heated 
by  a  small  bunsen  burner  with  a  pilot  flame,  so  that  when  the  re- 
quired temperature  is  reached  the  "pilot  flame  may  be  used  to  main- 
tain the  temperature  at  the  required  amount.  A  thermometer 
should  be  suspended  in  the  stain  and  the  beaker  containing  the 
stain  should  lie  as  small  as  possible  so  as  not  to  use  too  much 
stain  at  one  time. 

In  making  up  the  slides  for  this  staining  method  it  will  be 
necessary  to  use  the  dropper  method  as  used  by  Bright  and  also 
by  Spence.  (See  methods  of  making  up  microscope  slides  as  out- 
lined on  page  7.)  This  dropper  method  involves  dropping  a  dilute 
mixture  of  water  and  fibers  upon  the  slide  and  then  evaporating 
the  water.  The  dry  slide  is  then  ready  for  staining. 

Method   of   using   solutions   A   and   B    known   as   the   potassium 

ferric  ferricyanide  stain. 

Mix  equal  volumes  of  solutions  A  and  B,  heat  to  35°  C.  in  the 
water  bath,  regulating  the  pilot  flame  so  that  the  temperature  will 
remain  constant  within  1°  for  a  period  not  less  than  15  min.  The 
dry  slide  is  then  dipped  in  distilled  water  to  moisten  it  uniformly, 
so  that  air  bubbles  will  not  be  formed  when  it  is  immersed  in  the 
stain.  If  air  bubbles  are  formed  the  fibers  under  the  bubbles  will 
not  be  stained.  If  dipping  in  water  still  leaves  bubbles,  they  can 
be  removed  by  blowing  across  the  slide  from  the  edge.  The  slide 
is  then  suspended  in  the  stain  and  left  there  for  15  min.  at  35"  C. 
It  is  then  removed  and  washed,  by  dipping  in  and  out  of  a  beaker 
of  distilled  water  six  times  and  repeating  the  process  in  a  fresh 
beaker  of  water.  The  slide  can  then  be  placed  wet  into  the  red 
solution,  but  it  is  perhaps  better  to  dry  it  out  so  that  the  fibers 
will  be  stuck  on  tightly  again  in  case  they  have  been  loosened  to  any 
extent  by  the  treatment. 


Method  of  using  solution  C,  the  substantive  red  stain;  A  fresh 
solution  is  heated  to  45°  C.,  and  the  -slide,  after  moistening  and 
excluding  bubbles  as  before,  is  suspended  in  the  solution  for  five 
minutes  at  45"  C.  and  immediately  washed  in  two  beakers  of  dis- 
tilled water. 

The  slide  is  then  dried  and  a  cover  glass  placed  on  with  a  drop 
of  balsam. 

Directions  for  assuring  best  results :  To  get  the  clearest,  bright- 
est results,  distilled  water  must  be  used  throughout,  and  the  stain- 
ing solutions  must  be  fresh.  The  two  solutions  for  making  ferric 
ferricyanide  will  keep  well  if  placed  in  separate  'bottles.  Equal 
volumes  are  mixed  together  immediately  before  using.  The  red 
solution  should  be  freshly  made  each  time  for  the  best  results,  as 
it  gets  thick  and  stringy  on  standing,  especially  when  it  is  being 
_he_ated  up  continually. 

Staining  under  the  conditions  described  gives  an  unbleached  sul- 
phite perhaps  the  deepest  blue  it  is  possible  to  obtain  without 
depositing  blue  on  the  slide  and  on  the  bleached  sulphite;  the 
method  also  produces  the  best  red  on  the  bleached  fibers  without 
turning  the  unbleached  fibers  purple.  Unbleached  sulphite  from 
different  mills  varies  considerably  in  lignin  content,  hence  some 
samples  stain  a  deeper  blue  than  others.  The  foregoing  condi- 
tions give  a  satisfactory  blue  on  a  sample  of  high  grade  im- 
ported unbleached  pulp  as  well  as  a  better  color  on  the  average 
run  of  unbleached  pulps,  the  latter  being  not  so  well  cooked  as  a 
rule.  With  pulp  containing  more  lignin  it  is  possible  to  use  a 
slightly  stronger  treatment  with  the  red  and  thus  get  a  better 
color  on  the  bleached  without  affecting  the  unbleached. 

After  one  has  had  a  little  experience  with  the  method  he  can 
tell  by  the  color  of  the  unbleached  fiber  whether  he  may  safely 
continue  the  staining  with  the  red  for  six  or  possibly  seven  minutes 
at  45°  C.  At  first,  however,  it  is  better  to  follow  the  directions  as 
given.  It  is  of  prime  importance  to  wash  out  or  neutralize  every 
trace  of  alkali  in  the  fibers,  as  the  blue  is  decolorized  by  alkali. 

This  method  of  staining  will  in  general  give  a  distinction  be- 
tween pure  cellulose  fibers  and  those  which  contain  lignin.  Rags, 
bleached  sulphite,  soda  pulp  or  any  thoroughly  bleached  material 
are  stained  red  while  unbleached  sulphite,  mechanical  pulp,  jute,  or 
any  lignified  materials  are  stained  blue.  The  principal  application 
lies  in  the  estimation  of  unbleached  pulp  in  book  papers.  A  con- 
siderable saving  can  be  made  by  using  unbleached  sulphite  instead 
of  bleached,  hence.it  is  important  to  know  how  much  unbleached 
pulp  there  is  in  a  sheet. 

2. — Classification   of    Fibers    Used   in    Papermaking*    (143) 

For  convenience  in  studying  filters,  it  is  desirable  to  know  the 
relations  of  the  various  groups  and  the  accompanying  charts 
(Fig.  8)  indicate  the  arrangement  of  the  fibers  that  are  used  for 
papermaking.  It  is  to  be  understood  that  this  is  not  a  'botanical 
classification  and  the  standard  text  book  on  botany  is  to  be  con- 
sulted if  this  information  is  desired. 

CLASSIFICATION  OF  FIBERS  *(141) 

A  suggested  grouping  of  various  fibers  used  for  paper-making. 

A— Seed  hair  fiber (  £°"?n 

(  Bombax  wool — East  Indies 


B — Stem  fiber  (bast  family) 


C — Leaf  fiber. 


Flax  or  linen 

Hemp  (cool  temperate  climate) 

Jute 

f  Common  nettle 
Nettle  fibers,  i  China  grass 

[  Ramie  (water-resist! 


Sunn   (India) 
Straw  and   esparto 

New  Zealand  hemp 

Abaca 

Sisal  or 

Henequin    (Yucatan) 

Aloe  (South  America)  Piteira 

Pineapple  leaf  fiber 


ing) 


PAPER    TESTING    METHODS 


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PAPER    TESTING    METHODS 


D — Fruit    fiber Cocoanut  fiber 


E— Wood    fiber . 


Resinous  or  coniferous 


Non-resinous  or  broad- 
leaf 


FIG.  7 


Larch-Tamarack 

Fir 

Spruce 

Cedar 

Pine 

Hemlock 

Cypress 

Birch 
Mulberry 
Beech 
Gum 

Tulip  tree 
[_  Poplaf 


3.    Degree  of  Beating 

By  a  careful  examination  of  the  fibers  under  the  miscroscope, 
it  is  often  possible  to  determine  something  of  the  amount  of  'beat- 
ing to  which  the  stock  has  'been  subjected.  The  length  of  the 
fibers,  the  amount  that  the  ends  have  been  frayed  and  the  degree 
of  the  breaking  down  of  the  cell-walls  all  give  information  in  regard 
to  the  'beating  treatment.  It  is  necessary,  however,  to  have  con- 
siderable experience  'before  the  results  are  reliable.  The  use  of 
photomicrographs  assists  in  this  study  and  the  accompanying  plates 
indicate  some  of  the  characteristic  differences  of  fibers  and  in  beat- 
ing treatment. 

4.    Specks  or  Dirt  in  Paper 

The  appearance  of  a  sheet  may  show  imperfections  caused  by 
foreign  materials  or  malformation  on  the  wire.  These  are  the 
most  common  causes  of  poor-looking  paper. 

Generally,  specks  need  microscopic  examination.  A  Bausch  and 
Lomb  binocular  miscroscope  shown  in  Fig.  6  and  a  set  of  dis- 
secting needles  are  useful.  For  chemical  tests  on  small  particles 
small  test  tubes  made  by  sealing  one  end  of  small  glass  tubing 
are  convenient  if  the  reaction  is  to  be  watched  under  the  micro- 
scope. 

Rubber.  This  is  very  objectionable.  It  finds  its  way  into  the 
stock  along  with  rag  stock,  sometimes  as  rubber  paste  in  tire 
fabrics  and  the  like,  and  sometimes  in  paper  stock  as  rubber  bands 
from  office  waste. 

Under  the  magnifying  glass  rubber  specks  can  be  stretched  by 
pinning  down  one  end  with  a  dissecting  needle  and  pulling  out  the 
speck  with  another  needle  point. 

Rubber  specks  will  give  a  characteristic  rubber  odor  if  burned  by 
sticking  into  a  flame  on  the  end  of  a  needle.  They  are  soluble  in 
carbon  tetrachloride. 

Rosin  specks.  These  are  translucent  amber-colored  specks  so  re- 
sembling rosin  that  they  are  easily  recognized.  Proof  of  their  iden- 
tity can  be  had  by  dissolving  the  separated  speck  in  ether  in  a 
small  tube  so  that  the  action  can  be  watched  under  the  microscope. 
Qualitative  rosin  tests  can  be  applied  to  the  speck  as  given  under 
qualitative  tests  for  rosin. 

Other  specks  resembling  small  bark  particles  may  come  from 
size  which  was  made  from  impure  rosin  without  proper  filtration. 
Although  not  as  translucent  as  the  ordinary  rosin  speck  they  usually 
carry  enough  rosin  to  respond  to  the  qualitative  test. 

Wood  specks.  Chips  or  wood  fibers  which  might  result  from 
the  accidental  grinding  off  of  a  beater  paddle  or  similar  cause  can 
be  quickly  identified  by  applying  phloroglucinol ;  they  give  a  char- 
acteristic red  coloration  as  in  the  groundwood  test. 

Iron  specks.  Washer  or  'beater  bars,  jordans,  scaly  pipes,  cor- 
roded overhead  ironwork,  and  iron  buttons  from  rags  contribute 
iron  in  ;  metallic  or  oxidized  form  at  times.  The  metallic  particles 
will  be!  attracted  by  a  magnet  after  being  freed  from  the  sheet. 
The  scale  or  oxidized  iron  can  be  dissolved  in  concentrated  hydro- 
chloric acid  and  a  drop  of  potassium  sulphocyanate  added.  Iron 
gives  a  characteristic  wine-red  color.  This  test  can  be  applied  to 
the  separated  particle  in  a  small  tube,  or  the  sheet  suspected  to 
contain  iron  may  be  placed  on  a  glass  plate,  wetted  with  concen- 
trated hydrochloric  acid  for  five  minutes,  and  then  with  10  per  cent 


potassium  sulphocyanate  solution.  Each  iron  speck  shows  red  when 
the  sheet  is  held  up  to  the  light.  The  glass  plate  forms  a  con- 
convenient  holder  for  the  sheet.  The  red  color  fades  in  a  few  minute^ 
and  count  should  be  taken  immediately. 

Another  method  is  to  immerse  the  paper  in  2  per  cent  potassium 
ferrocyanide,  then  in  2  per  cent  acetic  acid,  then  wash  well  in  water. 
Hang  the  sheets  vertically  until  dry.  There  will  be  a  blue  coloration 
wherever  there  was  an  iron  speck  in  the  sheet.  This  method  makes 
a  more  permanent  record  than  the  sulphocyanate  treatment. 

Oil  spots.  Oil  spots  are  translucent  and  can  be  spread  or  thinned 
with  ether  or  chloroform.  Extraction  with  either  of  these  solvents 
removes  the  oil,  unless  it  is  of  a  peculiar  pasty  formation  caused  by 
use  of  oily  rags  in  the  stock.  Mineral  oil  in  rags  is  prone  to  form 
a  dirty  congealed  mass  in  the  washers,  which  specks  the  halfstuff 
with  black  specks  in  which  mineral  oil  is  the  binder.  Such  specks 
in  the  finished  sheet  are  not  entirely  removed  by  ether  or  chloro- 
form. They  are  slightly  translucent,  and  unaffected  by  solution  in 
concentrated  sulphuric  acid. 

Color  spots.  Poorly  ground  colors  such  as  poor  ultramarine  give 
a  fine  specky  appearance  usually  identified  by  color  only. 

Alum  spots.  These  are  usually  pulverized  by  the  pressure  of  the 
calender  rolls.  They  are  soluble  in  water  and  give  a  slight  acid 
reaction  with  indicators.  This  reaction  is  best  watched  by  dis- 
solving the  speck  in  a  very  small  test  tube  and  adding  the  indicator 
while  the  tube  is  under  the  microscope  and  against  a  white  back- 
ground. 

Coal  particles.  Coal  dust  is  insoluble  and  gives  no  color  reac- 
tions with  any  reagent.  In  appearance  iron  scale  can  be  mistaken 
for  it,  and  in  doubtful  cases  an  iron  test  should  be  made  on  the 
sheet  and  the  unaffected  black  particles  examined  for  coal. 

Under  the  microscope  it  can  be  seen  that  coal  particles  in  a 
calendered  sheet  have  been  so  pulverized  by  the  pressure  of  the 
rolls  that  they  shatter  very  easily  when  picked  with  a  dissecting 
needle.  Large  particles  give  a  characteristic  black  smear  when 
crushed  and  rubbed  across  the  sheet. 

Button  specks.  Bone  buttons  ground  by  beaters  or  jordans  into 
small  pieces  come  through  into  the  finished  sheet  as  a  light  colored 
powdered  spot  due  to  crushing  in  the  calenders.  A  hole  is  often 
made  at  a  button  speck  due  to  the  crushed  button  piercing  the  sheet 
and  then  partly  crumbling  out  after  calendering.  Such  specks  can 
be  differentiated  from  alum  as  they  are  insoluble  in  water  and  give 
no  acid  reaction  with  the  indicators. 

Paper  specks.  In  stock  made  from  old  papers  small  undefibered 
pieces  may  slide  through  the  screens  and  form  a  speck  on  the  sheet. 
Such  specks  are  fibrous  and  when  lifted  out  of  the  sheet  they  can 
'be  defibered  under  the  microscope  with  dissecting  needles,  showing 
their  identity  by  this  characteristic. 

Foam  spots.  Because  of  the  depression  left  after  each  foam 
bubble  there  is  a  circular  spot  more  translucent  than  the  rest  of 
the  sheet  formed  wherever  foam  bursts  on  the  partly  formed  sheet. 
The  result  is  characteristic,  circular,  and  translucent  as  a  small 
round  wa^rmark  would  look. 

Drag  spots.  Stock  adhering  to  the  slices  on  the  wire  forms 
small  uneven  lumps  when  it  drags  off  upon  the  sheet.  These  spots 
are  not  very  common  but  can  'be  recognized  as  an  irregular  forma- 
tion having  no  foreign  material  present. 

Knots.  Fabrics  in  rag  stock  with  knotted  threads  very  often, 
show  the  knots  in  the  finished  sheet.  The  knotted  thread  is  easily 
recognized  under  the  microscope. 

5.     Starch 

In  addition  to  chemical  tests  for  the  determination  of  starch  in 
paper,  it  is  possible  to  determine  the  kind  of  starch  used.  The 
various  untreated  starches  have  characteristic  shapes  and  markings 
which  may  easily  be  identified  under  the  microscope.  This  is  also 
possible  in  some  cases  with  treated  starches,  used  in  the  size-tub. 


PAPER    TESTING    METHODS 


17 


III.     PHYSICAL   TESTING 
1.     Effect  of  Relative  Humidity* 

A  superficial  examination  of  the  published  data  will  indicate  that 
the  physical  qualities  of  paper  are  affected  to  a  considerable  degree 


(a)  Relative  Humidity — The  moisture  content  of  the  test  sample 
is  affected  by  changes  in  humidity,  either  absolute  or  relative.  Ab- 
solute humidity  is  defined  as  the  number  of  grains  of  moisture  per 
cubic  foot  of  air  at  the  temperature  in  question.  Relative  humidity 
is  defined  as  the  percentage  of  moisture  present,  at  any  particular 


FIG.  9 

Aspen    (Populus  tremuhides) — xlOO — (Bureau  of  Standards). 
by   changes   of  the   moisture  content  of  the  test   sample.     Different 


FIG.  11 

Chestnut    (Castanca    diirtata) — xlOO — (Bureau   of    Standards). 


kinds  of  paper  as  well  as  different  qualities  are  affected  to  a  differ-      temperature,  to  the  amount  of  moisture  present  if  the  air  were  sat- 
iMit  degree,  but  certain  tendencies  are  obvious  and  the  importance  of      urated   9i  that   temperature.     The  available   data   seem  to  indicate 


the  consideration  of  the  condition  of  the  test  sample  at  the  time  of 


that  in  most  cases,  the  variation  of  quality  of  paper  bears  a  relation 
to  relative  humidity,   rather  than  to  absolute  humidity. 


FIG.  10 

Balsam    Fir    (Abies    balsamca) — xlOO — (Bureau    of    Standards). 

test  should  not  be  underestimated.  The  suggestions  contained  herein 
are  not  conclusive  nor  complete  but  the  conclusions  have  been  de- 
termined after  a  careful  study  of  existing  data. 


*  The  reader  is  referred  to  an  exhaustive  treatment  of  this  suhject  in  Tech- 
nical Association   Papers,  Series  VI    (1923). 


FIG.  12 

Hemlock   (Tsuga   canadensis) — xlOO — (Bureau   of  Standards). 
In    most    testing    laboratories    that'  attempt    to   control    their    at- 
mospheric conditions,  a  temperature  of  70°  F.  and  a  relative  humid- 
ity   of    65    per    cent    is    maintained.     These    conditions    have   ibeen 


18 


PAPER    TESTING     METHODS 


adopted  because  of  work  done  in  the  past  in  Germany  and  'because 
of  the  increased  cost  to  maintain  a  lower  relative  humidity  during 
the  warm  weather,  when  the  moisture  must  be  taken  out  of  the  air 
by  some  method  of  refrigeration.  It  is  not  uncommon,  however,  in 
steam  heated  rooms,  during  the  winter,  to  obtain  a  relative  humidity 
as  low  as  15  per  cent. 


and,  at  85  per  cent  relative  humidity,  the  range  is  from  9  to  14 
per  cent,  with  20  per  cent  as  a  possible  saturation  point  at  100 
per  cent  relative  humidity.  The  accompanying  curve  (Fig.  17)  in- 
dicates in  a  general  way  the  tendencies  of  change  of  moisture 
content  with  relative  humidity. 

(c)     Weight — In   general,   it   may   be   said   that  the   variation   of 


FIG.  13  FIG.  IS 

Fibers    from    Rag    Pulp — xlOO — (Bureau    of    Standards).  .  Spruce   Mechanical    Pulp    (Picca    canadensis) — xlOO — (Bureau   of    Standards'). 

(6)  Moisture — The  moisture  content  of  paper  increases  with  weight  due  to  changes  of  relative  humidity  is  similar  and  proper- 
increase  of  relative  humidity  and  in  -general  seems  to  be  independent  tional  to  the  variation  of  moisture  content  of  the  paper.  The  varia- 
of  the  furnish,  kind  of  paper,  or  the  method  of  test.  A  composite  t;on  jn  weight  from  15  per  cent  relative  humidity  to  85 -per  ct-nt 
average  with  the  moisture  content,  when  plotted,  as  ordinate  and  relative  humidity  seems  to  be  about  6  per  cent. 


• 


FIG.  16 

Tulip   Tree    (Liriodendron    tulipfera) — xlOO — (Bureau    of    Standards). 
(d)     Bursting  Strength — Data  available   at  this   time   in   regard 

lightly  concave     At   15   per  cent   relative  humidity,   the   moisture      to  the  effect  of  relative  humidity  upon  the  bursting  strength  seem 
content  varies  from  3  to  7  per  cent  for  different  kinds  of  paper      to  indicate  that  bursting  strength  increases  with  relative  humidity. 


FIG.   14 

Rice  Straw — xlOO — (Bureau  of  Standards), 
with   relative  humidity  as   the  abscissa  produces   a  regular  curve, 


PAPER    TESTING    METHODS 


19 


up  to  about  35  per  cent  relative  humidity  and  that  from  that  point 
decreases  equally  rapidly  with  increasing  relative  humidity.  This 
conclusion  seems  to  be  assured  from  the  considerable  amount  of 
data  available  but  it  is  not  believed  that  any  conversion  factor  may 
yet  be  developed.  The  amount  of  variation  is  widely  different  for 
different  papers  and  it  seems  to  'be  evident  that  long-fibered  papers 
are  affected  to  a  greater  extent  than  short-fibered  papers.  In  any 
case,  this  variation  is  quite  evident  and  should  be  taken  into  con- 
sideration when  careful  and  accurate  tests  are  to  !be  made. 

(e)  Tearing  Strength — Very  little  data  are  available  in  regard 
to  the  relation  between  tearing  strength  and  relative  humidity  but 
such  work  that  has  been  done  indicates  that  this  test  is  markedly 
affected  by  changes  of  relative  humidity.  Tearing  strength  in- 
creases to  a  considerable  extent  with  increase  of  relative  humidity 
and  the  amount  of  this  variation  seems  to  be  comparable  with 
that  in  the  case  of  the  folding  and  tensile  test. 

(/)  Folding  Endurance — The  effect  of  relative  humidity  upon 
this  test  seems  to  be  somewhat  erratic  -with  different  papers  but  in 
any  case  the  variation  is  very  marked.  In  general,  the  folding 
endurance  increases  rapidly  with  increase  of  relative  humidity,  the 
machine  direction  more  rapidly  than  the  cross  direction.  With 
certain  kinds  of  paper,  there  seems  to  be  a  peak  in  the  curve  at  80 
to  90  per  cent  relative  humidity  with  a  rapid  decline,  while  with 
other  papers,  this  peak  does  not  appear.  Data  seem  to  indicate 
that  this  test  is  affected  by  relative  humidity  to  a  greater  extent 
than  any  other. 

(g)  Breaking  or  Tensile  Strength — The  variation  in  this  test 
seems  to  be  very  similar  to  that  in  the  case  of  the  bursting  strength, 
but  to  a  greater  degree.  Strength  increases  with  relative  humidity 
up  to  a  point  of  about  35  per  cent  and  then  decreases  at  a  similar 
rate.  This  variation  is  similar  in  both  the  machine  and  cross  direc- 
tion and  in  either  case  seems  to  be  over  twice  as  much  as  in  the 
case  of  the  bursting  strength. 

2.     Characteristics  of  Paper 

(a)  Machine    Direction:    *(3)     Several    methods    are    available 
for  determinating  the  machine  direction  in  a  sample  of  paper.     It 
may  sometimes  be  ascertained  by  mere   inspection  of  the  sheet,  as 
the  formation   noted  on  looking  through  it   is   often  conclusive  to 
the  trained  observer. 

The  usual  machine  wire  imparts  to  the  sheet  of  paper  a  "wire 
mark"  consisting  of  a  series  of  diamond-shaped  marks,  the  long 
diagonal  of  which  points  in  the  machine  direction.  If  the  wire 
mark  is  sufficiently  prominent  so  that  its  direction  can  be  deter- 
mined this  will  establish  the  machine  direction. 

If  the  paper  is  well  sized  and  a  circular  piece  is  cut  out  and 
moistened  on  one  side  by  floating  on  water,  it  will  tend  to  roll  up 
into  a  cylinder  whose  axis  is  in  the  machine  direction  of  the  sheet. 
If  the  paper  is  unsized  it  will  become  entirely  soaked  through  on 
floating  on  water  and  will  not  curl  up.  This  may  be  avoided  by 
sizing  the  paper  with  an  alcoholic  solution  of  rosin  or  with  a 
solution  of  gelatine  in  water,  drying  and  then  making  the  test. 

Another  method  of  determining  the  machine  direction  is  to  cut 
two  narrow  strips  of  the  paper  one  from  either  direction,  place 
these  one  over  the  other  and  hold  them  upright  in  the  fingers. 
They  will  droop  over  of  their  own  weight  and  if  they  cling  close 
together  the  under  strip  is  in  the  machine  direction  while  if  the 
under  slip  falls  away  from  the  upper  the  latter  is  in  the  machine 
direction. 

The  form  of  the  break  made  by  the  Mullen  tester  shows  the 
machine  direction,  as  the  longest,  or  chief,  line  of  rupture  is  always 
across  the  sheet. 

(b)  Wire  or  Felt  Side.     *(3)    In  many  cases  this  may  be  de- 
termined  very   easily  by  a   simple   inspection   but   in   some   papers 
the  wire  marks  do  not  stand  out  at  all  plainly.     Sometimes  they 
may  be  made  more  prominent  by  plunging  the  sample  for  a  moment 
into  water  and  draining  or  blotting  off  the  excess.     The  moisture 
causes  the  fibers  to  expand,  thus  undoing  the  work  of  the  calenders 


and  resorting  the  texture  of  the  sheet  as  it  left  the  machine  wire. 
Inspection  of  a  sheet  thus  dampened  will  often  show  that  the  wire 
marks  stand  out  plainly,  where  before  they  were  indistinguishable. 
This  method  very  often  proves  satisfactory  even  for  coated 
papers. 

3.    Area  of  Sample 

For  convenience  use  a  straight  edge  graduated  into  inches  and 
tenths  and  read  to  hundredths  of  an  inch.  Calculate  area  in  square 
itiches. 

4.     Weight  of  Sample 

The  sheet-weighing  device  that   indicates  the  equivalent   weight 


FIG.  17.  MOISTURE  CONTENT  OF  PAPER 

A    curve    which    represents    the    relation    between    the    percentage    of    relative 

humidity   and  the  moisture  content   of  paper.      This   curve   is   a   composite  of 

data   obtained    from   several   sources   and   under  different   conditions. 

in  pounds  in  terms  of  a  500-sheet  ream,  is  most  suitable  for  labora- 
tory or  mill  use. 

In  weighing  very  small  samples,  it  is  not  desirable  to  use  a  weigh- 
ing device  graduated  in  terms  of  a  500-sheet  ream.  For  such  cases 
a  chemical  balance  should  'be  used  and  the  weight  in  grams  multi- 
plied by  1.102,  will  give  the  equivalent  weight  of  500  sheets  of  the 
size  weighed. 

Formula  for  sample  weight  on  sheet  paper  scales : 

(wt.   in   lb.)    X    (1,000) 

=  weight  25    X   40,500. 

Area   of  sheet    in   sq.   in. 

(wt.   in  Ib.)    X    (Area   of  trade  size   desired) 

=    wt.   of  trade  size  desired. 

..  Area  of  sheet  in  sq.  in. 

It  is  obvious  that  the  samples  being  weighed  must  be  accurately 
measured  to  determine  their  size,  and  this  is  done  by  means  of  an 
accurate  'rule,  graduated  in  tenths  of  an  inch.  The  following  formula 
is  of  assistance,  where  o  is  scale  reading,  6  is  one  dimension  of  the 
sample,  c  is  the  dimension  at  right  angles  to  b,  and  d  is  the  num- 
ber of  sheets  of  paper  in  the  sample: 

a  x  1,000 

.=   weight  in  lb.   per  ream  25    X   40,   500. 

b    X    c    X    d 

For  samples  of  paper  weighing  less  than  20  lb.  on  the  quadrant 
scale  a  chemical  balance  is  used.  For  convenience,  the  following 
formula  is  used : 


(Weight  in  grams)    X    (1,102)    X    (1,000) 


=    weight    in    Ibs.    per 


(Area  of  samples  in  sq.   in.)    X    (number  of  sheets) 
ream   25    X    40,   500. 

To  convert  the  weight  of  the  standard  ream  to  the  weight  of  a 
ream  of  the  desired  trade  size,  it  is  only  necessary  to  multiply  the 
weight  of  the  former  by  the  area  of  the  latter  and  divide  by  1,000, 
•provided,  of  course,  that  the  latter  ream  contain  500  sheets. 


20 


PAPER     TESTING     METHODS 


a.  Balances  and  Scales.     There  are  a  number  of  available  as  il- 
lustrated.   (Figs.  18,  19,  20,  21.)     They  may  be  calibrated  by  plac- 
ing small  accurate  weights  in  the  pan  and  taking  readings  on  the 
scale.     An  average  of  several  readings  at  uniform  distances  apart 
on  the  scale  should  be  obtained. 

b.  Conversion  Factors.    The  weight  of  a  ream  folio  size,  17  x  22, 
500,  can  be  stated  as  the  substance  number. 

A  method  for  determining  the  substance  number  on  small  samples 
by  the  analytical  balance  is  as  follows :  A  flat  piece  of  thin  metal 
cut  exactly  2  x  2-1/16  in.  is  held  upon  the  sample  and  a  sharp 
instrument  run  around  the  edge  of  the  metal.  The  sample  cut 
exactly  2  x'  2-1/16  in.  has  a  substance  number  equal  to  its  weight  in 
centigrams. 
Waight  in  centigrams  X  500  sheets  X  .374  sq.  in.  per  sheet 

45,360  centigrams  per  pound    X    4.125   sq.   in.   in  sample 
Weight  in   centigrams    X    178,000 


—   substance. 


=    substance   number. 
187,110 

TYPICAL     EQUIVALENT    WEIGHTS    IN  STANDARD     AND    TRADE 

SIZES* 

Weight  of  --earn,               Trade  size  Weight  of 

25   X  40,  500         ream,  500  sheets    Area  of  sheet  ream,  trade  size 

Lb.                                In.                             In.  Lb. 

52.6                      25    X   38  950.0  50 

64.2                        17    X   22  374.0  24 

100.0                      20   X   25  500.0  50 

15b.O                    22.5    X   28.5  641.3  100 

Conversion  between  ream  basis  weight  and  grams  per  square  meter. 

Weight  in  grams  pe'  square  meter  — 

(Weight  in  Ib.  of  any  ream,  500  sheets)    X   1406.13 

Area  of  sheet  in  sq.  in. 


FIG.  18.    QUADRANT  SCALE 

A  typical  scale    for   weighing  paper.      (Foreign  Paper  Mills,   Inc.,   New   York 

City). 


Wt.  in  Ib.  per  ream  of  500  sheets  = 

(Wt.   in   grams  per  square  meter)    X 


(Area  of   sheet  in  sq.  in.) 


1406.13 

To  convert  to'lb.  •    ,                Ream  size 

0.267,  17  x  22  500 

0.714  25  x   40  500 

0.429,.  .  20-x. 30  ... 

0.591  24  x  36  480 

0.675  -.25  x  38  500 

0.618  24  x  36  500 


To  convert  to  grams 
3.75 
1.40 
2.33 
1.69 
1.48 
1.62 


Length  of  paper  in  a  roll. 

Roll  weight  Ream  area  <sq.  in.). 

Length    in    ft.    =    -  X  — 


Ream  weight  X  roll  width 


12 


Ream  size 

17  x  22  500... 

25  x  38  500. . , 

25  x  40  500..  . 

20  x  26  500... 

20  x  30  480. . 

24  x  36  480... 


Factor 
15583 
38583 
41667 
21667 
24000 
34500 


5.     Bursting  Strength 

a.  Description — There  are  two  types  of  testers  available  for  de- 


FIG.  19.  TORSION  BALANCE 

A    balance    designed    on    the    torsion    principle,    and    with    scale    calibrated    in 
pounds  per  ream.      (Torsion   Balance  Co.,  New  York  City). 

termining  the  bursting  strength  of  paper  and  board.  One  is  of  the 
hydraulic  type  in  which  the  paper  is  clamped  against  a  rubber 
diaphragm,  through  which  the  pressure  is  applied  to  a  circular  area 
of  the  paper  measuring  approximately  1  sq.  in.  The  pressure  is 
indicated  on  a  special  Bourdon  tube  gage.  The  second  type  is  of 
the  spring  operated  metal  plunger  design  in  which  the  paper  is 
clamped  between  annular  rings,  through  which  a  spring  operated 
plunger  is  forced. 

b.  Comparison — Although  a  large  amount  of  data  have  'been  col- 
lected by  individual  laboratories  with  the  instruments  shown  in  the 
accompanying   photographs    (Figs.   22,   23,   24)    very   little   informa- 
tion has  been  published.     Certain  conclusions,  however,  may  be  as- 
sumed and  certain  recommendations  made.     There  is  very  little,  if 
any,   relation    between   the   data   obtained   with   these   three   testers. 
With  averages  of  equal  number  of  tests,  the  variation  seems  to  be  in- 
versely proportional  to  the  diameter  of  contact.     There  is  no  stand- 
ard   method    of    manipulation    to    assist    various    laboratories     in 
duplicating   results.      There    is   no    fundamental    unit   to    which    the 
testers  may  be  referred   for  calibration.      In   addition   to  this,   little 
attention  is  given  to  the  care  of  these  testers  and  in  the  case  of  the 
Mullen  tester,  the  deterioration  of  the  diaphragm  is  often  neglected, 
as  well  as  calibration  of  the  gage.     It  is  recommended  that  a  defi- 
nite method  of  making  these  tests  be  determined  upon  and  precau- 
tion given  for  the  care  of  the  testers.      In   any   case,  the  bursting 
strength  of  a  sample  as  reported  should  be  the  average  ot  not   less 
than  ten  individual  tests. 

c.  Ratio — The  bursting  strength  test  to  be  of  greatest  use  must 
U  expressed  in  terms  of  the  weight  of  the  sample.     This  ratio  of 


PAPER     TESTING     METHODS 


21 


strength  to  weight  may  then  be  directly  compared  with  the  strength 
ratio  of  any  other  paper. 

The  strength  ratio  may  be  expressed  as  a  percentage. 
Bursting  strength  X  100 


Streng'.h  ratio  =: 


Wt.  in  Ib.  (on  a  size  25  x  40,  500) 
6.     Thickness 


a.  Description — The  thickness  of  a  paper  may  best  be  determined 
by  the  use  of  a  spring  micrometer  having  a  hand  that  travels 
around  a  circular  dial.  This  dial  is  graduated  into  thousandths  of 
an  inch.  This  direct  reading  type  of  thickness  gage  should  not 
be  read  closer  than  half  of  a  thousandth,  as  they  are  not  accurate 
beyond  that  point.  The  following  is  a  list  of  manufacturers  of  this 
type  of  thickness  gage :  B.  C.  Ames  Co..  Waltham,  Mass. ;  B.  F. 
Perkins  &  Son,  Inc.,  Holynke,  Mass.;  Storrs  &  Bement  Co..  140 
Federal  Street,  Boston,  Mass. ;  The  Ashcroft  Mfg.  Co.,  85  Liberty 


FIG.  20.     SIIKET  WKIGHING  DEVICE 

An    accurately    made    delicate    balance    for    weighing   paper.      (Thwing    Instru- 
ment   Co.,    Philadelphia,    Pa.) 

Street,  New  York ;  Cornelius  Kahlen,  349  Broadway,  New  York ; 
E.  J.  Cady  &  Co..  Chicago,  111. 

It  is  advisable  to  have  all  thickness  gages  calibrated  before  use. 
This  may  best  be  done  by  securing  a  set  of  standard  sheet  metal 
leaf  gages,  which  range  from  0.001  to  0.01S  inch.  This  range  of  leaf 
gages  covers  the  ordinary  range  needed  in  testing  most  papers,  and 
should  be  used  periodically  to  see  that  the  instrument  for  measuring 
thickness  remains  accurate. 

For  the  purpose  of  obtaining  a  quick  comparison  of  the  relative 


compactness  of  several  papers,  the  following  formula  is  suggested : 

Thickness  in  thousandths  of  an  inch 

—   X    10,000  =    Relative  cc  mpactncss. 
"  (Weight  25  x  40,  500) 

The  factor  10,000  serves  to  give  a  resultant  figure  more  rapidly 
remembered.  A  very  highly  compressed  paper  may  show  a  rela- 
tive-compactness of  0.600,  while  a  very  spongy  or  fluffy  sheet  may 
bulk  to  1.300.  This  last  sheet  is  more  than  twice  as  'bulky  as  the 
former  mentioned. 

b.    Variations — A   superficial   inspection   of  the  different   types   of 


FIG.  21.     PEA  AND  BEAM   SCALE 

A  typical   scale  for   rough  work  for  use   in  the  machine   room, 
Co.,  New  York  City). 


(Fairbanks  & 


microrreter  gages  available  for  determining  the  thickness  of  paper, 
indicates  that  there  is  litt.e  or  no  uniformity  in  their  construction. 
It  is  found  that  there  are  considerable  differences  in  spring  pres- 
sure, in  size  and  shape  of  the  contact  areas  and  in  the  size  of  the 
dial  divisions.  It  would  seem  that  these  differences  would  affect 
the  accuracy  of  the  test  when  different  gages  are  used  and  it  is, 
therefore,  emphasized  that  the  test  is  not  accurate  closer  than  one- 
half  of  a  thousandth  of  an  inch. 

7.     Bulk 

The  bulk  of  paper  is  the  thickness  of  a  certain  number  of 
pages  and  applies  more  particularly  to  book  papers  where  the 
printer  desires  a  book  of  a  certain  number  of  pages  to  'bulk  one 
inch.  The  bulk  of  a  paper  is  measured  by  cutting  out  short  strips 
01  paper,  piling  them  up  to  the  required  number  and  measuring  the 
combined  height  of  the  pack.  This  measurement  may  be  made  by 
the  use  of  a  Perkins  bulk  tester  (Fig.  26).  This  instrument  meas- 
ures the  bulk  in  inches,  also  the  pressure  of  clamping,  and  takes  the 
place  of  the  ordinary  graduated  sliding  clamp  which  is  in  common 
use.  In  specifying  the  bulk  of  a  paper,  where  the  hand  clamp  is 
used,  it  is  necessary  to  specify  whether  heavy,  medium  or  light 
pressure  is  used.  In  using  the  Perkins  'bulk  tester,  the  pressure  is 
specified  in  pounds  per  square  inch,  as  indicated  on  the  dial. 

8.     Folding  Endurance 

a.  Description*  (S3).  The  folding  endurancePof'a  paper  is  meas- 
ured on  a  machine  in  which  a  strip  of  paper  of  "definite  width  and 
length  is  clamped.  The  clamps  are  held  apart  under  definite  ten- 
sion arid  the  paper  i^  caused  to  haid.  back  and  forth  upon  itself, 
until  the  fibers  wear!  ithrough  :at  the  line  "of  folding.  The  number 
of  double  folds  is  recorded  automatically. 


22 


PAPER     TESTING     METHODS 


The  folding  strength  of  paper  is  dependent  not  only  upon  the 
strength  and  durability  of  the  paper,  but  also  is  very  largely  in- 
fluenced by  th6  relative  humidity.  To  perform  this  test  in  the 
most  accurate  manner  it  is  therefore  necessary  to  keep  the  relative 
humidity  constant  for  all  tests.  This  can  only  be  done  by  making 
the  test  in  a  room  where  the  humidity  is  under  control.  Where 
such  a  room  is  not  available  then  note  must  be  made  of  the  per  cent 
relative  humidity  of  the  air  at  the  time  of  the  test.  No  tests  should 
be  attempted  when  the  humidity  is  either  very  high  or  very  low. 
A  relative  humidity  between  65  and  70  per  cent  is  more  easily 
attained  throughout  the  year  and  is  the  standard  humidity  recom- 
mended by  the  paper  testing  committee. 

The  folding  factor  is  determined  by  the  following  formula : 


Folding  endurance 


—  =   Folding  factor. 


(weight  25   x  40,   500) 

The  folding  factor  will  vary  between  about  0.1  and  200. 

b.  Calibration.  The  machine  illustrated  (Fig.  28)  was  designed  at 
the  Bureau  of  Standards  for  the  purpose  of  calibrating  the  springs 
acting  on  the  clamping  jaws.  It  consists  of  a  stand  on  one  end 
of  which  the  tester  can  be  screwed  firmly.  On  the  other  end  is  pro- 
vided a  support,  with  leveling  screws,  on  which  may  be  mounted 
a  wheel  provided  with  knife-edge  bearings.  Around  the  rim  of  the 
wheel  is  a  groove  of  about  *4  m-  deeP-  This  wheel  should  be  made 
of  three  plies  of  wood,  glued  to  prevent  warping,  and  should  be  so 
balanced  that  when  mounted  on  the  supports  with  the  back  of  the 
knife  edge  horizontal,  it  will  remain  in  any  position  within  45 
degrees  either  side  of  this  without  tending  to  rotate.  The  table  on 
which  the  folding  tester  is  mounted  should  be  made  large  enough 
so  that  the  machine  can  be  set  up  with  either  jaw  facing  the  large 
grooved  pulley.  The  relation  between  the  height  of  this  table  and 
that  of  the  'bearings  for  the  knife  edge  supporting  the  grooved 
pulley  should  be  such  that  a  fine  piece  of  thread  resting  on  the  base 
of  the  groove  in  the  pulley  and  attached  to  the  center  of  one  of 
the  clamping  jaws,  the  other  clamp  being  removed  entirely,  will 
form  a  horizontal  line.  After  the  jaws  have  been  properly  marked 
for  maximum  extension  according  to  Reid,  Veitch  and  Sammet,  one 
of  the  jaws  with  its  spring  holder  and  stand  should  be  removed 


FIG.  22.     MULLEN  BURSTING  TESTER  *(89) 

A  hydraulically   operated  bursting  tester   in   which  the  pressure   is   applied  to 

the   paper   through    a    rubber    diaphragm   and    indicated    on    a    gage.      (B.    F. 

Perkins  &  Sons,  Holyoke,  Mass.) 

entirely  from  the  machine  and  the  latter  should  then  be  mounted 
with  the  end  without  the  jaw  and  spring  toward  the  grooved  pulley. 
A  thread  or  very  fine  wire  should  'be  attached  to  the  center  of  the 
clamping  jaw,  passed  through  the  reciprocating  slot  (the  latter 
being  locked  in  its  neutral  position)  over  the  wheel,  and  tied  to  a 


FIG.  23.    ASHCROFT  TESTER 

A    spring    operated   metal    plunger    bursting   tester.      (Ashcroft    Manufacturing 
Co.,   New  York  City). 

1  kg.  weight  so  that  the  latter  swings  free,  and  the  thread  falls 
entirely  in  the  plane  of  the  groove  in  the  pulley.  If  the  reciprocat- 
ing part  be  locked  in  its  neutral  position  and  the  alignment  of  the 
machine  and  pulley  be  carefully  made,  it  will  be  unnecessary  to  re- 


FIG.  24.     WEBB  TESTER 

A  device  developed  for  testing  corrugated  and  solid  fiber  container  board.  It 
is  of  the  spring  operated  metal  plunger  design.  (Container  Club,  Chicago.) 

move  that  part  of  the  machine  which  carries  the  four  small  rollers 
and  through  which  the  reciprocating  part  passes.  After  setting  up, 
care  should  be  taken  that  the  thread  holding  the  weight  does  not 
touch  any  part  of  the  folding  tester  and  that  the  square  shank  of 
the  jaw  is  entirely  free  from  any  contact  with  the  sides  of  the 


PAPER    TESTING    METHODS 


23 


square  opening  into  which  it  fits.  If  the  spring  tension  is  correct 
the  jaw  will  be  drawn  out  by  the  action  of  the  1  kg.  weight  so  that 
the  mark  previously  made  to  the  square  shank  will  be  just  visible. 
If  this  is  not  the  case  the  spring  tension  should  be  adjusted  by 
loosening  the  small  set  screw  holding  the  knurled  collar  on  the  end 
opposite  the  jaw,  after  which  the  tension  is  adjusted  by  revolving 
this  knurled  collar.  The  other  jaw  should  be  adjusted  in  the  same 
way  after  reversing  the  machine,  removing  the  jaw  just  calibrated 
and  replacing  the  other. 

c.  .-Iccnracy.  In  view  of  the  fact  that  the  folding  test  is  prac- 
tically confined  to  a  test  strip  IS  mm.  long  and  about  0.25  mm.  wide, 
that  wearing  parts  tend  to  make  it  difficult  to  maintain  uniform 
conditions  of  the  tester  and  because  of  the  very  marked  effect  of 
changes  of  relative  humidity,  it  is  probable  that  the  variations  be- 
tween averages  of  ten  tests,  either  on  the  same  machine  or  on 
.different  machines,  will  vary  from  5  to  15  per  cent  under  ideal 
•conditions  and  that  this  variation  will  be  considerably  greater  under 
the  normal  testing  methods.  It  is  recommended  that  an  average  of 
.ijot  less  than  ten  test's  on  the  sample  in  one  direction  be  obtained 
-to  indicate  the  folding  endurance  in  that  direction. 

Nc.te--In  connection  with  the  folding  tester,  attention  should  be  called  to 
the  fact  that  it  is  absolutely  essential  that  the  small  steel  wheels  supporting 
the  clamping  jaws  be  perfectly  round,  well  oiled  and  revo'lve  easily,  as  the 
jaws  move  back  and  forth.  In  one  case  the  fact  that  one  of  these  did  not 
l evolve  t:uiisv*d  an  error  if  25  per  cent  in  the  results. 

GREEN    FOLDING  TESTER 

This  folding  tester  (  Fig.  29)  was  originally  devised  to  apply  to 
a.  pulp  sheet  made  either  in  the  hand  mo!d  or  by  means  of  the  standard 
pulp  sheet  mold.  The  folding  tester  is,  therefore,  applicable  to  any 
sheet  product,  irrespective  of  bulk  or  tensile  strength.  It  consists  of 
two  planes  of  hardened  steel,  ground  true,  which  abut  along  a 
straight  line,  accurate  to  ground  fit.  These  two  planes  have  a  slight 
inclination  downward  from  the  line  along  _which  they  abut.  .They 
are  pressed  together  along  this  line  by  means  of  springs,  set  to  a 
specified  tension.  Running  over  these  planes  are  two  rollers,  each 
parallel  with  the  line  along  which  the  planes  abut,  set  a  fixed  dis- 
tance apart,  and  pressing  downward  on  the  planes  by  a  known  force, 
which  is  fixed  by  the  adjustment  of  springs.  By  means  of  constant 
.speed  electric  drive,  the  rolls  are  run  backward  and  forward  across 


FIG.  25.     THICKNESS  TESTER  *(89) 

A  typical  micrometer   gage  for   testing  the   thickness  of  paper. 
Bement   Co.,   Boston,    Mass.) 


(A.    Storrs   & 


FIG.  26.     BULK  TESTER 

A   useful   apparatus    fcr   determining  the   bulk   or  the  number   of  pages  to   an 
inch   of  a    particular   kind   of   paper.      (B.    F.   Perkins   &   Sons,  Inc.,   Holyoke, 

Mass.) 

is  the  moment   when  the   specimen  has  been  severed  at  its  center, 
not  when  it  has  been  severed  entirely. 


the  line  along  which  the  two  inclined  planes  abut  and  the  specimen 
under  test  is  held  between  the  planes  under  known  and  constant 
pressure.  There  is  an  automatic  counting  attachment  which  regis- 
ters the  number  of  double  folds  of  the  specimen.  The  end  point 


FIG.  27.     FOLDING  TESTER 

A   device   for  determining  the   folding   endurance  of  a   strip  of  paper   15   mm. 
wide  under  a  tension  of  1   kg.      (Foreign  Paper  Mills,  Inc.,  New  York) 

9.    Tensile  or  Breaking  Strength 

o.    Description.    The  tensile  strength  of  paper  is  determined  by 
the  load,  in  pounds,  required  to  break  a  strip  of  paper.    The  tensile 


24 


PAPER    TESTING    METHODS 


strength  machine,  best  known  in  the  paper  industry,  is  the  Schopper 
tensile  machine   (Fig.  30). 

In  this  device  a  strip  of  paper  15  mm.  (approximately  19/32  in.) 
wide  by  180  mm.  long  (approximately  7  3/16  in.)  is  clamped  at 
each  end  and  the  clamps  are  moved  apart  until  the  strip  is  broken. 
A  suitable  device  indicates  the  pull  in  kilograms  '(approximately  2.2 
Ib.)  required  to  break  the  strip.  As  the  English  units  of  measure- 
ments are  used  on  all  other  tests,  it  is  recommended  that  the  load  in 
kilograms  per  15  mm.  width  strip,  be  converted  into  pounds  per 
inch  of  width  by  the  following  formula : 

(3.73)    X'  (Tensile   strength   in    kg.    per    15    mm.    width)    =    Tensile   strength 
in  Ib.  per   1   in.  width. 

A  tensile  strength  factor  may  be  determined  by  the  following 
formula : 

(Tensile    strength    in    Ib.    per    in.    width) 

-    =:    Tensile    strength    factor. 
(Weight  25x40,  500) 

The  usual  factor  for  tensile  strength  is  known  as  the  breaking 
length.  This  is  the  length  of  a  strip  which,  if  suspended  at  one 
end,  would  break  of  its  own  weight.  The  following  formula  may 
be  used  to  determine  the  breaking  length  of  a  sample : 

(Tensile  strength  per  1    in.  width)    X    (13,889) 

—    =    Breaking   length    in    yds. 
(Weight  of  a  sheet  25x40,  500) 
(Tensile  strength  per   15   mm.  width)    X    (13,899    X    3.73) 


length  in  yds. 


(Weight  25x40,  500) 


=    Breaking 


The  breaking  length  factor  will  range  from  a  maximum  of  about 
11,000  yards  down  to  approximately  2,000  yards. 

In  this  test  certain  precautions  should  be  observed  in  order  to 
get  accurate  results.  The  width  of  the  sample,  the  rate  of  apply- 
ing the  load  and  the  alignment  of  the  sample  in  the  jaws  will  affect 
the  test.  Care  should  be  exercised  that  the  test  strip  should  be 
cut  accurately  to  the  prescribed  width  and  that  it  should  be  cut 
accurately  parallel  to  either  the  machine  or  cross  direction  of  the 
paper.  It  is  recommended  that  the  lower  jaw  be  moved  at  a  rate 
of  12  in.  per  minute  for  the  50  kg.  tester.  The  test  strip  should 
be  carefully  inserted  in  the  jaws,  so  that  the  pull  is  straight,  since 
otherwise,  a  tearing  strain  will  be  introduced  that  will  produce  an 
error.  It  is  further  recommended  that  the  tester  should  'be  cali- 
brated and,  if  necessary,  a  correction  curve  and  formula  be  derived. 

b.  Wet  Tensile*  (122).  This  test  may  be  performed  on  the  same 
apparatus  as  for  the  dry  tensile  strength  with  certain  modifications. 
Due  to  the  weakness  of  paper  when  wet,  it  is  desirable  to  make 
the  apparatus  more  sensitive  and  this  is  done  by  removing  the 
weight  at  the  bottom  of  the  moving  arm,  calibrating  the  tester 


FIG.  29.    GREEN  FOLDING  TESTER 

Star  Brass  Manufacturing  Co.,  Boston,   Mass. 


v    •  FIG.  28.     CALIBRATING  DEVICE- 

An    arrangement    designed    for    the   purpose   of    calibrating   the    spring   tension 
of  the  Schopper  folding  tester.     (Bureau  of  Standards,  Washington,  D.  C.) 


FIG.  30.    SCHOPPER  TENSILE  TESTER 

Tensile  tester   operated   hydraulically   with   device   for  determining   the  elonga- 
tion   of   the    paper.      (Foreign    Paper    Mills,    Inc.,    New    York) 


PAPER     TESTING     METHODS 


25 


under  this  new  condition  and  obtaining  a  correction  curve  or  factor 
for  conversion.  It  is  recommended  that  a  speed  of  6  in.  per  minute 
be  applied  to  the  lower  jaw  and  that  this  be  kept  uniform.  It  is 
recommended  that  'before  testing,  the  strips  shall  be  immersed  in 
water  at  70°  F.  for  20  minutes  and  that  these  conditions  be 
rigidly  observed,  as  the  test  is  markedly  influenced  by  both  the 
temperature  of  the  water  and  the  time  of  immersion.  Since  the 
test  strips,  after  wetting,  are  easily  injured  and  are  difficult  to 
place  in  the  jaws  in  true  alignment,  extra  care  is  necessary. 
;  c.  Stress  Strain*  (20).  In  connection  with  the  determination  of 
the  breaking  strength  of  heavy  bag  papers,  it  has  been  indicated 
that  a  study  of  the  stretch  due  to  repeated  application  of  load  is 
of  considerable  importance  in  indicating  the  quality  of  the  sample 
for  this  purpose.  The  tensile  strength  of  the  paper  is  determined, 
using  a  strip  1  in.  wide  and  12  in.  long,  the  load  being  applied 
at  the  rate  of  12  in.  per  minute.  By  means  of  a  recording  device, 
shown  in  the  accompanying  photograph  (Fig.  31),  the  stretch  of 
the  sample  under  repeated  loads  (10  per  cent  less  than  the  average 
breaking  strength)  is  indicated  and  it  is  possible  to  determine  the 
stretch,  regain  and  elasticity  of  the  sample  by  this  method. 

d.  Elongation  at  Rupture.  Most  of  the  tensile  test  devices  are 
equipped  with  a  secondary  scale  to  indicate  the  stretch  or  elonga- 
tion at  the  time  of  rupture.  This  secondary  quadrant  has  two 
scales  and  gives  the  stretch  in  mm.  or,  if  a  test  strip  of  180  mm. 
between  jaws  was  used,  in  percentage  stretch.  Data  available 
seem  to  indicate,  however,  that  this  elongation  at  rupture  has  little 
significance  in  evaluating  a  test  sample. 

10.    Absorption 

a.     Strip*    (6).     The  absorption  of  a  blotting  paper  is  indicated 


FIG.   32.     PERKINS   TENSILE   TESTER 


A  tensile  tester  recently  brought  out  by  B.  F.   Perkins  &  Son, 
Holyoke,   Mass. 

by  the  height  in  mm.  to  which,  in  a  given  time,  a  liquid  will 
rise  by  capillary  action,  when  one  end  of  a  strip  of  paper  held 
vertically  is  immersed  in  water.  The  height  in  mm.  to  which  the 
liquid  (preferably  water)  will  rise  in  10  min.  is  taken  as  a  measure 
of  the  relative  absorption  of  the  paper. 

In  making  this  test,  using  the  'strip'  method  (Fig.  33),  a  strip  of 
blotting  paper  15  mm.  (about  3/5  in.)  wide  and  ISO  mm.  (about 
6  in.)  long  is  suspended,  so  that  the  lower  end  dips  3  mm.  (about 
Y%  in.)  into  a  pan  of  distilled  water.  Besides  the  strip  is  a  scale 
reading  in  mm.  (fractions  of  an  inch),  and  at  the  end  of  each 
minute  for  10  minutes  readings  are  taken  of  the  height  to  which 
the  liquid  rises  in  the  strip.  Five  tests  are  made  in  both  the 
"machine"  and  "cross"  direction  and  an  average  obtained.  The 
result  is  reported  as  the  height  to  which  the  liquid  will  rise  in  10 
min.  When  necessary,  or  advisable,  the  same  strips  may  'be  sub- 
jected repeatedly  to  the  test,  which  will  indicate  the  decreasing 
ability  to  absorb  water  or  ink.  In  addition,  a  standard  ink  of 
the  following  formula  may  be  used : 


Grams 
23.4 
7.7 
30.0 
25.0 
1.0 
2.2 


FIG.  31.     STRESS  STRAIN  TESTER 

A  hydraulically  operated  200  kg.  Schopper  tensile  tester  with  recording  drum 
to  indicate  the  stretch  on  the  repeated  load.  (Bureau  of  Standards;  Foreign 
Paper  Mills,  Inc.,  New  York.) 


Tannic    acid    (dry) 

Gallic    acid     (crystals) 

Ferrous    sulphate     (crystals) 

Dilute  hydrochloric  and -(U.  S.  P.r  sp.  gr.   1.049;   10%   HC1  by  weight 

Phenol 

Bavarian  blue,  S.  &  J.  No.  478  or  similar  suitable  dye 

Water  to  make  a  volume  of  1,000  cc.  at   15,6°   C. 

Note — Any  water-soluble  basic  aniline  blue',  as  Niagara  3B,  National  Aniline 
Company,  may  be  used  in  place  of  Bavarian  blue. 

b.  Pipette*  (13).  In  this  test  a  1  cc, -pipette  js  employed  and 
is  suspended  in  such  a  way  that  the  end  of  the  pipette  is  l/2  in. 
from  the  surface  of  the  test  sample  of  blotter.  The  test  sample 
cut  4  in.  square  is  laid  felt  side  up  upon  a  coarse  wire  screen, 
which  is  supported  by  a  large  beaker.  This  is  done  to  prevent  as 
far  as  possible  the  blotting  paper  from  caving  in  at  the  center  where 
the  liquid  fell  upon  it.  (The  felt  side  of  paper  is  the  top  side  of 
the  paper  as  it  leaves  the  paper  machine  wire.)  Both  distilled  water 


26 


PAPER    TESTING    METHODS 


and  the  above-mentioned  government  standard  ink  are  used  at  the 
three  temperatures  of  60,  70,  and  80°   F. 

A  stop  watch  is  used  to  measure  the  time  it  took  the  1  cc.  of 
liquid  to.  leave  the  pipette  until  it  is  totally  absorbed  by  the  paper. 
Also  the  diameter  of  the  circular  spot  on  the  paper  was  measured 
immediately  at  the  completion  of  the  time  reading. 

c.  Total  Absorption*   (23).     By  means  of  this  test,  test  samples 
cut  2  in.  square  are  first  weighed  on  a  chemical  balance  and  then 
dropped  with  the  felt  side  down  on  a  trough  of  distilled  water  and 
also  on  a  trough  of  government  standard  ink.     The  same  tempera- 
tures are   used   for  the   ink   and   water  as   in  previous   absorbency 
tests.     After  a   10  minute  period  of  absorption,   the   samples  were 
taken  out,  drained   l/2   minute  and  again   weighed  to  determine  the 
amount  of  liquid  absorbed. 

d.  Blotting  Test*  (23).     In  this  test,  small  strips  of  blotting  paper 
cut  l/2  in.  wide  by  4  in.  long  are  used  to  'blot  signatures  that  are 


ernment  standard  ink  is  used  as  in  previous  tests  and  a  record  is 
kept  of  the  number  of  times  each  test  sample  will  blot  the  signature 
before  the  ink  shows  signs  of  spreading  on  the  paper.  The  felt  side 
of  both  blotting  and  bond  paper  is  used  throughout  the  tests,  and 


FIG.  33.    ABSORPTION  TEST 

A    convenient    method    of    making    a    number    of   absorption    tests    of   blotting 
paper  by  the    Klemm   method.      (Bureau    of   Standards) 

written  with  a  stub  pen  on  ordinary  bond  paper.  The  same  signa- 
ture is  used  throughout  the  test  and  only  one  signature  is  blotted 
at  a  time.  The  small  size  of  the  test  sample  causes  each  Wot  to 
be  made  on  almost  the  identical  spot  in  the  blotting  paper.  Gov- 


FIG. 34.     RELATION  BETWEEN  FILLER  AND  BLOTTING  QUALITY 

Curves    representing   the    variation    of    a    practical    blotting    test    with    the 
percentage   of  clay   in  the  paper 

an  average  of  three  tests  is  taken  as  a  final  result  for  each  blotting 
paper. 

It  is  interesting  to  note  in  the  accompanying  curves  (Fig.  34)  that 
there  seems  to  be  an  inverse  proportion  between  the  amount  of  ash 
of  the  paper  and  the  number  of  times  that  the  test  strip  may  be  used 
before  the  ink  begins  to  spread. 

11.     Opacity  and  Translucency*  (142) 

The  opacity  or  translucency  of  a  paper  may  be  measured  by  the 
"contrast  ratio"  method  as  described  in  Bureau  of  Standards  Circu- 
lar No.  63  (Fig.  35). 

The  Bureau  of  Standards  has  developed  and  adopted  a  standard 
method  for  determining  the  transparency  of  paper  and  tracing  cloth, 
which  is  described  in  detail  in  Circular  No.  63.  Briefly,  this  method 
consists  in  placing  a  sample  of  the  -paper  or  cloth  to  be  tested  over 
two  adjacent  surfaces,  one  white,  and  the  other  black,  and  measur- 
ing the  reduction  in  contrast  of  the  appearance  of  the  two  surfaces. 
If  the  material  in  question  is  quite  transparent,  the  contrast  between 
the  black  and  white  surfaces,  as  seen  through  the  material,  will 
be  quite  noticeable ;  but  if  the  material  is  opaque,  none  of  the  light 
incident  upon  its  surface  will  be  transmitted  and  absorbed  by  the 
black  surface  beneath,  and  consequently,  there  will  be  no  contrast 
'between  the  parts  of  the  material  covering  the  black  and  white 
surfaces. 

In  making  the  measurements,  one  must  use  a  photometer  having 
a  divided  photometric  field,  one-half  of  which  is  illuminated  by  the 
light  coming  from  the  material  over  the  white  surface,  while  the 
other  half  is  illuminated  by  the  light  coming  from  the  material 
over  the  black  surface.  The  two  halves  of  the  photometric  field 
are  then  "matched"  by  usual  observation  and  properly  setting  the 
photometer,  and  the  indicated  results  recorded.  A  slight  computa- 
tion based  on  these  observations,  gives  the  numerical  measurement 
sought,  which  is  called  the  contrast  ratio.  It  varies  between  zero 
and  unity,  larger  values  indicating  less  transparency. 

12.     Tearing  Test 

A  continued  and  increasing  interest  in  the  determination  of  the 
tearing  strength  of  paper  by  some  mechanical  means  has  produced 


PAPER     TESTING     METHODS 


27 


various  devices  for  this  purpose.  A  'brief  description  of  several  is 
given,  but  there  is  not  as  yet  sufficient  data  available  to  make  any 
recommendations  in  regard  to  those  which  are  most  satisfactory. 

a.  Knife  Edge  Method*    (133).     In  the  tester  perfected  at  the 
A.  D.  Little,  Inc.,  Laboratory,  the  sample  to  be  tested  is  clamped 
to  the  baseboard  of  the  instrument.     The  clamp  has  a  knife  edge 
along  one  side  and  the  paper  is  torn  along  this  edge.     The  tear  is 
first   started  slightly   and  the  end  of   this   strip   is  clamped   to  the 
movable  arm  which  is  connected  to  a  bellows  arrangement  with  a 
pressure   gage.    The    arm,   bellows    and   gage   are   mounted    on    a 
movable  carriage,  operated  on  an  inclined  track  by  means  of  a  lug 
screw.     As  this  screw  is  made  to  revolve,  the  carriage  moves  up  the 
incline  and,  as  one  end  of  the  paper  is  attached  to  the  movable  arm, 
the  tearing  is  accomplished.     The  force  necessary  to  tear  the  paper 
is  determined  by  the  pressure  shown  on  the  gage. 

b.  Witham  and   Case   Testers.     Both  these  testers  are  based  on 
the  principle  that  the  force  necessary  to  tear  the  sample  is  applied 
by   running   water   into   a  beaker   which   may  be   connected  to   the 
sample  in  any  one  of  several  ways.     In  the  Witham  tester*   (136, 
148),  this  load  is  applied  by  means  of  running  water  from  a  burette 
into  a  beaker,  set  on  one  end  of  the  pivoted  arm.  the  opposite  end 
of  which  is  attached  to  the  sample.     In  the  Case  tester*   (128),  the 
movable  clamp  is  merely  a  spring  clothes-pin,  to  which  is  attached 
a   small   bucket.     Water    is    run    into   the  bucket   until    the    sample 
is  torn. 

e.  Schofifer*  (129).  The  heavy  counter- weight  of  the  Schopper 
tensile  tester  (Fig.  38)  is  removed,  the  test  sample  is  cut'l  in.  wide 
and  4  in.  long,  slit  down  the  middle  about  2  in.,  and  one  of  the 
slit  ends  is  placed  in  each  of  the  jaws.  The  pawls  on  the  rack 
are  raised,  the  lower  jaw  lowered  at  a  uniform  rate  and  readings 
taken  at  intervals  of  10  sec.  As  in  the  case  of  the  wet  tensile 
test,  the  tester  must  be  calibrated  for  the  new  conditions  and  to 
avoid  a  tubbing  effect  when  several  plies  are  used,  the  lower  jaw 
may  be  offset  as  indicated  in  the  accompanying  photograph. 

d.  Elmeiidorf*  "(131,  134).  The  principle  upon  which  this  tester 
{Fig.  37)  is  based  is  the  fact  that  the  tearing  force  is  determined 


test  sample  is  recommended  and  care  must  be  exercised  that  the 
width  of  the  test  sample  is  exact  and  the  placing  of  it  in  the  jaws 
is  carefully  performed.  The  tester  is  calibrated  for  16  plies  of 
paper  and  if  any  other  number  is  used,  the  necessary  lactor  must 
be  applied. 


FIG.  35.    OPACITY  APPARATUS 

A    device    for    measuring   the    opacity    or    translucency    of   paper    by    contrast- 
ratio   method.      (Bureau  of   Standards) 

indirectly  by  means  of  the  work  required  to  tear  a  sheet  of  paper. 
The  moving  segment  of  the  instrument  may  be  considered  to  be  a 
pendulum,  whose  swing  is  retarded  by  the  tearing  of  the  paper. 
The  tearing  force  is  determined  from  the  relation  existing  between 
work,  length  of  tear  and  force.  More  than  one  ply  of  paper  in  the 


FIG.  36.     WITHAM  TEARING  TESTER 

An   early   type   of   tearing   tester   developed   for   the   use  of  testing  bag   paper. 
(G.    S.    Witham,    Sr.,    Hudscn    Falls,   N.    Y.) 

e.  Discussion  of  the  Tearing  Test.  Available  data  seem  to  indi- 
cate that  there  are  a  number  of  factors  which  influence  the  results 
obtained  in  making  this  test  'by  any  of  the  above-mentioned  methods. 
These  factors  are:  (1)  width  of  sample  and  width  of  paper  on 
cither  side  of  the  tear,  (2)  the  number  of  sheets  or  plies  torn  at 
one  time,  and  (3)  the  relative  humidity  at  which  the  tests  are  made. 
Sufficient  data  are  not  available  for  conclusions  to  be  reached  in 
regard  to  these  factors  and  it  is,  therefore,  impossible  at  this  time  to 
make  any  recommendations  in  regard  to  the  efficiency  or  accuracy 
of  these  methods  or  to  interpret  the  data  obtained. 

13.     Degree  of  Sizing 

Several  methods  have  'been  proposed  for  determining  the  sizing 
quality  of  paper.  Practically  all  of  these  methods  are  merely  com- 
parative and  a  recent  series  of  tests  indicated  that  no  two  lab- 
oratories or  observers  would  grade  various  samples  even  in  the  same 
order.  The  chief  criticism  of  the  majority  of  the  methods  used 
is  that  no  account  is  taken  of  the  thickness  of  the  paper. 

a.  Floiation  Methods.  A  simple  qualitative  test  to  indicate  the 
effectiveness  of  the  sizing  as  a  preventive  of  the  absorption  of  ink, 
may  be  made  by  using  the  Ink  Flotation  Test  *(110).  This  method 
involves  the  drawing  of  a  strip  of  paper  over  the  surface  of  an 
iron  tannate  ink  and  allowing  it  to  drain  and  dry  naturally.  Upon 
examination  of  the  surface  with  a  low-power  microscope,  a  well- 


28 


PAPER     TESTING     METHODS 


sized  paper  will  show  no  indication  of  the  fiber  having  absorbed 
the  ink.  Any  variation  in  the  depth  of  color  on  the;  surface  will 
indicate  a  lack  of  uniform  sizing.  This  test  may  be  still  further 
developed  by  erasing  the  surface  with  an  ink  eraser  (a  spun  glass 
eraser  is  most  suitable)  and  again  dipping  the  sheet  as  before. 
A  paper  well  sized  throughout  the  sheet  will  show  little  or  no 
additional  absorption  of  ink  at  the  erased  spot.  This  test  is  only 
comparative  but  may  be  valuable  to  a 'mill  ii^  checking  the  daily 
progress. 

;  I'^r  comparative  sizing  effect,  squares  2  by.  .2  in.  are  cut  from 
each  sample.  These  are  subjected  for  at  least  30  min.'.to  the  same 
atmospheric  conditions.  Each  square  is  then.-  dropped  upon  an 
ink  bath  and  the  time  in  seconds  recorded  from  the  moment  the 
sample  touches  the  ink  to  the  penetration  of  ink  through  the  upper 
surface  of  the  sheet.  The  average  of  an  equal  number  of  deter- 
minations, at  least  six,  is  used  for  comparative  sizing  effect  in  each 
sample.  It  is  absolutely  essential  that  comparative  tests  be  made 
under  identical  atmospheric  conditions  and  by  the  same  operator, 
because  atmospheric  moisture  and  the  ink  bath  temperature  may 
greatly  influence  the  penetration  of  the  paper  and  different  people 
have  different  judgments  as  to  when  the  ink  is  through. 
The  ink  used  for  the  above  test  is  made  as  follows : 

Tannic  acid    (dry) 23.4  gr. 

Gallic   acid    (crystals)    7.7  <jr. 

Ferrous  sulphate   (crystal) 30.0  gr. 

Dilute  hydrochloric  acid   (U.   S.   P.;   sp.   gr.    1.049;    10%   HCI   by 

weight) 25.0  cc. 

Phenol 1.0  gr. 

Blue   dye    (Bavarian   Blue  S  &  J  No.   478) 2.2  gr. 

Water  to  make  up  to  1,000  cc.,  allow  to  settle,  and  decant  from  any  sediment. 

Note — Any  water-soluble  basic  aniline  "blue,  as  Niagara  3B,  National  Aniline 
Company,  may  be  used  in   place  of  Bavarian  blue. 

Keep  the  temperature  of  the  ink  constant.     Use  the  ink  but  once. 
b.    Electrolytic   Method.    *(105,     112).     Since     1917    there    has 


ance  as  the  electrolyte  penetrates  the  sample.  The  sample  of  paper 
is  clamped  in  the  cell  unit,  which  is  itself  a  part  of  a  wheatstone 
bridge.  The  accompanying  photograph  (Fig.  40)  illustrates  the 
various  parts  of  a  rather  elaborate  outfit.  In  this  case,  a  recording 


FIG.  37.    ELMENDORF  TEARING  TESTER 

A   pendulum   type  of  tearing   tester   which   measures  the   work  done  in   tearing 
several  strips  of  paper.      (Thwing  Instrument  Company,  Philadelphia,   Pa.) 

been  an  increasing  interest  and  use  of  the  conductivity  or  electro- 
lytic method  for  determining  the  sizing  quality  of  paper.  There 
have  been  a  number  of  variations  of  the  principle  first  proposed 
by  Okell  but  they  are  all  modifications  to  attempt  to  make  the 
method  of  more  value  and  to  make  it  possible  to  interpret  the  data 
obtained. 

.When. a  sheet  of  paper  between  two  electrodes  is  surrounded  by 
an  electrolyte  and  an  alternating  current  is  passed  through  the 
whole,  there  follows  a  decreasing  resistance  or  increasing  conduct- 


FIG.  38.    Sciioi'i'ER  TEARING  TESTER  *(129) 

A  tensile  tester  adapted  for  making  tt-nrinn  tests  with  the  heavy  weight  re- 
moved ,'iiul  with  an  off-set  lower  jaw.  (Foreign  Paper  Mills,  Inc.,  Xow 
York.) 

drum  is  attached  so  that  the  data  are  plotted  as  a  curve.  The 
value  of  this  method  is  that,  in  principle  it  may  be  made  very  ac- 
curate, the  curves  .may  lie  reproduced  with  test  samples  from  the 
same  sheet,  and  the  curve  always  presents  a  very  regular  aspect. 
The  method  is  of  considerable  value  as  a  control  method  during 
mill  runs,  after  a  curve  has  been  determined  for  a  particular  kind 
and  weight  of  paper.  It  due*  not  srem  possible,  however,  with  the 
limited  data  available  to  recommend  the  method  for  general  use 
and  it  is  doubtful  that  the  data  can  be  interpreted  in  terms  of  any 
fundamental  unit. 

A  practical  laboratory  instniim-nt  recently  developed  is  shown  in 
Fig.  39. 

c.  Siiifkifit  Mt'lliiHl.  KetViviicr  is  made  to  a  method  for  de- 
termining si/iiiy  quality  found  in  Wochcnblatt  fiir  1'apicrfabri- 
kolwn,  1920,  p.  39  (translation,  Paper,  -March  10,  1920),  by  Fritz 
Stockigt.  The  method  involves  floating  a  piece  of  paper  to  be 
tested  on  a  2  per  cent  solution  of  ammonium  thiocyanate 
(NH.CNS)  and  applying  to  the  upper  surface  a  1  per  cent  solu- 
tion of  ferric  chloride  (FeCL)  as  an  indicator. 

14.     Finish  or  Gloss*   (56) 

a.  Ingfrsol!  (.Hni-iinctcr.  The  glarimeter  (invented  and  developed 
by  L.  R.  Ingersoll  for  the  Forest  Products  Laboratory),  is  an  in- 


PAPER    TESTING     METHODS 


29 


strument  for  measuring  the  gloss  or  degree  of  finish  of  paper.  It 
depends  in  principle  on  the  fact  that  light  reflected  at  an  oblique 
angle  from  a  sheet  of  paper  is  partially  polarized,  the  degree  of 
polarization  depending  on  the  gloss  and  being  taken  as  a  measure 
of  it. 

The  way  in  which  this  principle  is  applied  is  made  clear  by  the 
diagram  (Fig.  42).  Unpolarized  (ordinary)  light  from  the  lamp  is 
partially  polarized  on  reflection  trom  the  sample  of  paper,  P,  and 
then  enters  the  polarimeter  or  "glariscope,"  which  consists  of  a  slit, 
S,  quartz  Wollaston  double-image  prism,  W,  lens,  L,  and  small 
nicol  prism,  N,  mounted  in  a  divided  circle.  The  eye  at  E  sees  a 
field  of  view  divided  into  two  parts  illuminated  respectively  by 
the  diffusely  and  specularly  reflected  light  from  the  paper,  and  the 
diffusely  reflected  light  alone.  A  setting  is  made  by  turning  the 
nicol  until  the  two  halves  are  equally  bright  when  the  gloss  may 
be  read  at  once  from  the  divided  circle.  On  the  scale  chosen  white 
blotting  paper  reads  about  "20  degrees  gloss,"  ordinary  machine 
finish  around  30  and  high  supercalendered  about  40.  The  highest 
gloss  on  white  paper  runs  about  SO  degrees. 

The  instrument  furnishes  a  ready  means  for  the  control  of  the 
supercalendering  process  and  renders  possible  uniformity  of  prod- 
uct. Readings  require  only  a  few  seconds  of  time  and  may  be  made 
by  an  almost  inexperienced  operator  and  in  an  ordinarily  lighted 
room.  Colored  papers  may  also  be  tested  if  a  suitably  colored  glass 
is  placed  in  the  eyepiece. 

b.  Martins-Koenig  Photometer.  The  accompanying  cut  (Fig.  43) 
of  the  type  of  photometer  used  in  connection  with  the  determina- 
tion of  finish  and  translucency  of  paper  is  given  because  of  the 


out.  The  weight  of  a  cubic  centimeter  of  the  paper  is  first  ascer- 
tained 'by  calculation  from  the  thickness  of  the  sample  and  the 
weight  of  a  •measured  area.  The  percentage  by  weight  of  the  vari- 
ous materials  present,  fibers,  clay,  size,  etc.,  is  then  determined  in 
the  usual  way  and  from  this  the  weight  of  each  in  a  cubic  centi- 


FIG.  39.     VALLEY  SIZE  TESTKK 
(Valley  Iron  Works,  Appleton,  Wis.  > 

increasing  interest  in  the  use  of  these  instruments.  The  scale. 
which  is  engraved  on  a  platinoid  circle,  is  divided  into  angular  de- 
grees and  densities.  It  is  understood  that  this  .type  of  photometers  .is 
to  be  produced  in  this  country. 

15.     Volumetric  Composition*   (3) 

The  determination  of  the  volume  composition  of,  a  paper   is  at 
best  only  an  approximation  but  it  is  at  times  desirable'  to  carry  it 


Fie.  40.    SIZING  TEST  APPARATUS*  (112) 

An  elaborate  set-up  with  recording  drum  for  the  study  of  the  electrolytic 
method  of  determining  the  sizing  quality  of  paper.  (Bureau  of  Standards.) 

meter  of  the  paper  is  calculated.  The  weight  of  each  substance  in 
grams  divided  by  its  specific  gravity  gives  the  volume  occupied  by 
it,  and  the  sum  of  all  of  these  volumes  subtracted  from  1.0  gives 
the  volume  of  air  per  cubic  centimeter  of  paper.  This  method  is 
fairly  accurate  when  only  fibers,  clay  and  rosin  are  present  but  when 
other  substances  are  added  as  in  coated  papers,  the  problem  becomes 
more  complex  and  the  results  less  reliable. 

If  the  volume  of  air  per  cubic  centimeter  of  paper  is-  the  only 
information  needed  it  may  be  obtained  by  determining  the  actual 
.••pecific  gravity  by  weighing  in  air  and  then  in  oil  of  known  density 
exactly  as  in  making  specific  gravity  determinations  in  water.  It 
will  be  found  necessary  to  expose  the  paper,  submerged  in  oil,  to 
reduce  pressure  for  some  time  in  order  to  be  sure  that  all  air  is 
removed  and  replaced  by  oil. 

16.     Retention  of  Loading 

By  retention  of  loading  is  .meant  that '  per  cent  of  the  entire 
amount  of  loading  material  added  to  the  beater,  that  is  retained 
in  the  finished  product. 

Secure  about  a  5-lb.  sample  of  the  filler  to  be  used,  being  careful 
to  select  a  representative  sample.  Break  up  all  lumps,  spread  on 
a  flat  surface,  divide  into  four  parts,  by  dividing  the  pile  by  two 
lines  at  right  angles  to  each  other  crossing  at  the  center  of  the  pile. 
Select  two  opposite  quarters,  mix  and  proceed  as  before.  This  is 
known  as  the  "quartering  method  of  sampling."  This  quartering 
method  is  continued  until  about  25  g.  of  loading  material  is  ob- 
tained, which  is  then  placed  in  a  bottle  for  further  use.  From  this 
bottle,  remove  a  1  g.  sample,  dry  at  105°  C.,  to  constant  weight 
and  calculate  per  cent  of  moisture  in  the  loading  material.  Place 
the  dried  residue  in  a  crucible  and  heat 'at  the  full  heat  of  a 
meker  burner  until  a  constant  weight  is  secured,  then  calculate  the 
per  cent  of  water  of.  composition  in  the  dry  clay. 

(Have  clay  in  a  finely  divided  state  and  stir  frequently  during 
burning.) 

Secure  sample  of  pulps  to  be  used  and  determine  per  cent  of 
moisture  and  per  cent  of  ash.  Weigh  the  pulp  added  to  the  beater. 
Weigh  the  clay  added  to  the  beater.  After  running  the  paper  over 
the  paper  machine,  secure  several  pieces  as  a  representative  sample, 
dry  and  make  the  ash  determination  on  the  paper.  The  above 


30 


PAPER     TESTING     METHODS 


mentioned  data   used   in   the    following    formula    will   give   the   per 
cent  of  clay  used  and  the  per  cent  retention. 

Let  P  =  weight  of  pulp  added   (in  Ih.) 
C  =  weight  of  clay  added    (in.   Ib. ) 
'A  =   Per   cent   ash  in   the  finished   paper. 
Ap  =   Per   cent  ash   in   the   pulp. 
We   =   Per  cent  water  of  composition   in  the   clay. 
Mp  =   Per   cent    moisture   in   the   pulp. 
Me  =  Per  cent  moisture  in  the  clay. 

100  X  C 

(1)  %  of  clay  used  =  

P 

100  A  X  P 

(2)  %    retention   =  — 

C  (100— A) 

100  C  (I— Me) 

(3)  %  of  clay  used  =  

P  (1— Mp) 
100P  X  (A— K) 

(4)  %   retention   =  

C  (100— A— K) 

The  value  of  K  is  the  per  cent  of  filler  not  derived  from  the  load- 
ing added.  An  average  value  of  K  is  0.50  so  that  the  formula 
(4)  may  'be  used  as  above  or  as  follows : 

100  P  (A— 0.5) 


(5)   %   retention  = 


C  (100— A— 0:05 

Formulas  (3)  and  (5)  are  recommended  for  use  by  the  Tech- 
nical Association  of  the  Pulp  and  Paper  Industry,  though  (1)  and 
(2)  may  be  used  when  accuracy  is  not  essential  or  when  the  values 
for  moisture  content  are  unknown.  Formula  (4)  does  not  take 
into  consideration  the  per  cent  water  of  composition  in  the  loading. 
Where  this  is  known  suitable  correction  may  be  made. 

No  account  is  taken  of  the  ash  from  alum  or  rosin  size  as  the 
maximum  amount  from  these  factors  is  probably  under  0.05  per 
cent-  and  therefore  negligible.  An  ash  determination  need  not  be 


Fie.  41.    GLARIMF.TKK 

A   device   developed   by    L.    R.    Ingersoll    for   the   purpose    of   measuring    the 
finish  or  gloss  of  paper.      (Central   Scientific   Company,  Chicago.) 


calculated   beyond  the  first  decimal  place.     (See  ash   determination 
under  chemical  testing.) 

An  alternate  retention  formula,  developed  in  the  laboratory  of 
the  S.  D.  Warren  Company,  Cumberland  Mills,  Maine,  is  suggested 
as  being  of  value,  as  it  may  be  used  without  making  tests  that 
interfere  with  production  of  paper. 

A  =  Per  cent  of  ash  in  air-dry  stock  going  to  machine. 
B  =   Per  cent  of  ash  in  air-dry  paper  at  reeJ. 
C   —   Per  cent  of  bone  dry   filler  lost  on  ignition. 
0.94  B  (100— 100  C— A) 

Retention  —  

A  (100— 100  C— B) 
A  and  B  are  considered  as  whole  numbers  and  C  as  a  decimal. 


17.     Conducting  Particles 

To  show  the  presence  of  conducting  particles  in  paper  0.5  or 
0.75  mils  thick,  the  sample  is  placed  upon  a  metal  plate  which  has 
been  polished  to  a  smooth  plane  surface.  This  plate  is  connected 
in  series  with  3  dry  cells,  a  model  280  Weston  voltmeter  of  3-volt 
range  or  a  similar  instrument,  and  a  metal  piece  which  has  a  per- 
fectly flat  under  surface  and  will  be  in  contact  with  all  parts  of  the 
plate  upon  which  it  rests.  This  metal  piece  is  about  1  in.  long  and 
l/2  in.  wide  and  is  attached  to  a  handle  for  convenience  in  using. 


FIG.  42.     GLARIMETER   PRINCIPLE 

Cut  showing  the  arrangement  of  lenses  and  the  principle  of  the  Ingersoll 
glarimeter.  (L.  R.  Ingersoll.) 

It  is  called  the  detector.  To  test  paper,  place  a  measured  area  upon 
the  plate,  make  contact  with  the  metal  detector  and  the  plate  and 
if  there  is  deflection  of  the  voltmeter  indicating  that  the  voltmeter 
will  show  any  drop  in  potential  that  occur  when  a  conductor  is  be- 
tween the  plate  and  the  movable  detector,  the  instrument  is  ready 
to  use.  Pass  the  detector  slowly  over  the  paper  on  the  plate,  using 
light  pressure.  When  a  deflection  of  the  voltmeter  indicates  that 
there  is  a  conducting  particle  in  the  sheet  between  the  detector  and 
the  plate,  the  position  of  the  detector  is  marked  and  it  is  then 
moved  over  the  spot  at  right  angles  to  its  former  position  and  the 
paper  marked  and  it  is  then  moved  over  the  spot  at  right  angles  to 
its  former  position  and  the  paper  marked  again  when  deflection 
occurs.  This  locates  the  particles  within  a  half-inch  square  and 
makes  it  available  for  microscopic  study.  Results  are  expressed 
in  terms  of  number  of  conducting  particles  present  per  sq.  ft.  of 
paper.  This  instrument  is  intended  for  papers  of  0.75  mil  thick- 
ness or  Jess.  With  thicker  papers,  the  particles  cannot  be  registered 
with  dependable  accuracy  because  they  seldom  extend  through  the 
full  thickness  of  the  sheet.  Comparison  of  iron  particles  present  as 
shown  by  chemical  tests  give  numbers  far  in  excess  of  the  number 
of  iron  particles  that  are  actual  conductors  in  the  sense  of  spoiling 
the  paper  for  electrical  purposes.  This  instrument  is  intended  for 
use  in  testing  papers  specified  for  use  in  electrical  equipment. 

An  additional  method  is  indicated  by  the  accompanying  photo- 
graph (Fig.  44).  The  small  metal  piece  in  the  foreground  is  used 
as  a  detector  and  the  presence  of  a  conducting  particle  is  indicated 
by  a  click  in  the  telephone  receivers. 

18.     Resistance  to  Water  Penetration 

Various  simple  methods  have  been  proposed  for  this  purpose  and 
they  are  included  as  they  may  be  of  some  assistance. 

A  quart  mason  jar  is  used  in  the  test.  A  circular  hole  of  1  in. 
in  diameter  is  cut  in  the  metal  top  and  the  bottom  of  the  jar  is 
broken  out.  The  sample  to  be  tested  is  placed  in  the  metal  top, 
between  the  rubber  washer  and  the  metal  and  firmly  screwed  in 
place.  The  jar  may  either  be  filled  with  water  or  may  be  re- 
versed and  partially  immersed  in  water.  The  temperature  of  the 
water  should  be  75°  F.  The  length  of  time  for  penetration  of  the 
water  will  indicate  a  relative  resistance. 

As  in  the  above  case,  a  circular  hole  of  1  in.  in  diameter  is 
cut  in  the  metal  top,  the  sample  placed  in  the  top  between  the  rub- 
ber washer  and  the  metal,  a  bone-dry  weighed  sample  of  absorbent 
cotton  or  paper  is  suspended  in  the  jar,  the  lid  put  on  and  the  jar 
reversed  and  partially  immersed  in  water  at  70°  F.  After  a  prede- 


PAPER     TESTING     METHODS 


31 


termined  length  of  time,  the  absorbent  cotton  or  paper  is  removed 
and  immediately  weighed.  The  increase  in  weight  will  indicate  a 
relative  value  for  moisture  penetration. 

A  modification  of  the  Stockigt  method  may  also  be  used  as  a 
means  of  determining  the  relative  water  resisting  quality  of  paper. 
For  routine  tests,  the  samples  may  conveniently  be  cut  about  21/* 
in.  square  and  molded  into  a  cup-shape  in  the  top  of  a  bottle  by 
depressing  the  paper  into  the  top  of  the  bottle  with  the  stopper. 
The  top  of  the  bottle  should  be  about  V/2  in.  inside  diameter. 
A  ground  glass  bottle  and  stopper  are  best  suited  to  the  purpose. 
At  least  three  test  "cups"  should  be  prepared  from  each  sample  to 
be  tested  and  the  average  result  taken  as  an  indication  of  the  degree 
of  water-proofing.  A  number  of  samples  may  be  tested  at  the  same 
time  by  using  a  wide  flat-bottom  pan  or  dish.  Enough  of  the  2  per 
cent  ammonium  thiocyanate  (NH4CNS)  solution  to  cover  the  bot- 
tom of  the  dish  and  float  the  "cups"  is  used.  After  the  "cups"  have 
been  floated  and  the  time  recorded,,  place  three  or  four  drops  of  the 
1  per  cent  ferric  chloride  ( FeCl3)  solution  in  the  middle  of  each 
cup  as  quickly  as  possible,  taking  care  not  to  drop  any  of  it  into 
the  other  solution.  A  large  dropper  is-  convenient  to  use.  Spread 
the  ferric  chloride  out  over  the  bottom  of  ea-.-h  cup  with  a  glass 
rod,  taking  care  not  to  spread  it  out  far  enough  to  touch  the  bend. 
For  where  the  paper  is  bent  or  folded,  the  solution  will  penetrate 
more  rapidly  and  give  erroneous  results.  The  layer  of  ferric 
chloride  solution  should  be  fairly  thin  because  it  has  a  reddish  color 
and  may  interfere  with  one's  judgment  of  the.  reaction  if  it  is  too 
thick.  The  time  required  for  the  pink  or  red  coloration  to  set  in 
is  taken  as  a  measure  of  the  degree  of  water-proofing.  On  samples 
it  will  be  found  that  only  a  single  point  of  color  is  seen.  This  is 
probably  due  to  a  "pin  hole"  or  fault  and  should  be  noted,  but  not 
taken  as  the  "end  point."  The  color  should  be  fairly  general  and 
pronounced  before  the  solution  is  considered  through. 

Note-^-Fritz  Stockigt,  Wochenblatt  fiii-  Pnpierfabrikation,  1920,  pg.  39; 
translation  Paper,  March  10,  1920. 


C 


^ 


TAPPED  HOLES  TOR  STAND. 


FIG.  43.     MARTIXS-KOENIG  PHOTOMETER 

A  sketch  of  a  photometer  used  for  Ingerscll  glarimeter.  (Courtesy  of  Adam 
Ililger,  Limited,  London.) 

IV.     CHEMICAL  ANALYSIS 
1.     Ash  Determination 

(a)  Quantitative— A  1  g.  sample  of  the  paper  to  be  tested 
is  burned  in  a  porcelain  or  nickel  crucible.  A  Meker  burner 
is  very  convenient  for  this  purpose,  as  some  heavily  loaded  papers 
require  considerable  time  and  heat  to  burn  the  last  traces  of 
carbon.  Ordinarily  a  white  paper  will  give  a  white  ash,  but  if 
mineral  pigments  have  been  used  the  ash  is  likely  to  be  colored. 
In  any  case  the  ash  should  be  free  from  specks  of  unburned  carbon. 

During  the  burning  care  must  be  taken  that  a  portion  of  the  ash 


is  not  lost  by  air  currents.     The  ash  is  often  light  and  fluffy,  and 
the  strong  currents  of  air  from  the  burners  may  blow  away  a  por- 

Note — The  sample  of  paper  need  not  be  weighed  closer  than  0.005  g.,  since 
a  1  per  cent  variation  in  the  moisture  content  will  introduce  an  error  of  0.01  g. 
If  the  maximum  error  in  the  weight  of  the  paper  is  0.01  g.  then  the  maximum 
error  in  the  weight  of  the  ash  will  be  0.01  g.  for  every  10  per  cent  of  ash 
present.  Therefore  in  a  paper  containing  10  per  cent  ash,  the  results  will  be 
reported  to  the  nearest  tenth.  If  special  accuracy  is  required,  the  paper  may 
be  weighed  in  the  bone  dry  condition.  Then  with  the  error  due  to  moisture 
eliminated  it  is  possible  to  weigh  the  paper  to  4-  0.0005  g.  and  the  error  will 
be  0.0001  g.  for  every  10  per  cent  of  ash.  The  results  may  then  be  reported 


to  the  nearest  hundredth.     This  latter  result  will  of  course  be  1  per  cent  lower 
1  g.  sample  containing  10  per  cent  of  moisture. 


than  the  ash  results  on  a 


FIG.  44.     CONDUCTING  PARTICLES 

An  arrangement  for  easily  determining  the  presence  of  conducting  particles 
in  thin  paper,  such  as  condenser  paper.  (Pittsfield  Works  Laboratory,  Gen- 
eral Electric  Company.)  (Bureau  of  Standards.) 

tion  of  it.  While  cooling  they  may  be  kept  in  a  dessicator,  but 
this  is  not  necessary,  since  the  ash  may  be  poured  into  a  counter- 
poised aluminum  pan  as  soon  as  the  crucible  is  cool  enough 
to  avoid  the  danger  of  loss  from  convection  currents.  The  ash  will 
cool  almost  instantly  and  may  be  weighed  at  once.  This  saves  the 
time  required  for  the  crucible  to  cool  and  also  avoids  the  necessity 
of  weighing  the  crucible. 

Note — Aluminum  is  recommended  as  being  less  easily  broken  as  well  as 
lighter,  than  glass. 

The  ash  as  finally  obtained  includes  all  non-volatile  and  non- 
combustible  matter  in  the  paper.  It  may  be  derived  from  at  least 
five  sources  : 

(1) — The  ash  of  the  pulp  from  which  the  paper  was  made;  (2) 
the  ash  from  the  various  loading  or  filling  materials  added;  (3) 
the  ash  from  any  surface  coating  or  sizing,  and  (4)  the  ash  of 
mineral  coloring  materials  or  pigments,  and  (5)  the  ash  derived 
from  alum  used,  though  the  amount  traceable  to  this  cause  is  very 
small  and  may  be  neglected.  The  complete  quantitative  analysis 
of  an  ash  is  a  time-consuming  and  also  a  rather  complicated  pro- 
cess. It  is  possible,  however,  to  obtain  some  idea  of  the  composition 
of  the  ash  by  a  few  comparatively  simple  tests. 

Once  the  paper  is  burned  it  is  impossible  to  tell  which  portion  of 
the  ash  is  derived  from  the  coating  and  which  portion  is  derived 
from  the  filler.  Therefore,  if  anything  more  than  the  total  ash 
content  is  desired  the  coating  must  be  stripped  from  the  paper 
before  ashing.  In  the  case  of  coated  papers  where  casein  has  been 
used  as  the  adhesive,  this  can  often  be  done  by  the  use  of  dilute 
ammonia.  The  insoluble  material  may  be  filtered  off,  dried  and 
weighed.  The  filtrate  may  be  evaporated  to  dryness  and  the 
residue  weighed.  This  will  include  the  casein  (or  soluble  casemates 
if  such  be  present)  as  well  as  any  soluble  material  present.  The 
difference  between  the  weight  of  the  total  ash  and  the  ash  of  the 


32 


PAPER    TESTING     METHODS 


paper  from  which  the  coating  has  been  stripped  plus  the  weight 
of  the  coating  will  give  the  weight  of  the  combustible  portion  (i.  e. 
glue  or  casein)  of  the  coating. 

Note — Provided  the  insoluble  portion  of  the  coating  has  been  ignited  to  the 
same  extent  as  the  total  ash. 

It  is  quite  possible  for  a  paper  to  have  an  ash  of  3  to  5  per 
cent  without  being  loaded.  This  might  be  due  to  the  ash  in  the 
pulp,  as  well  as  to  the  ash  derived  from  water  color,  alum  and  sizing 
materials. 

Where  the  ash  is  5  to  20  per  cent  the  paper  is  loaded.  A  list 
published  in  Paper  *(70)  gives  the  names  of  twenty-one  loading 
materials.  However,  from  the  chemical  standpoint  many  of  these 
are  practically  the  same  material  sold  tuidcr  different  names. 
They  are  all  silicates,  sulphates  or  carbonates  of  aluminum,  mag- 
nesium, barium  or  calcium.  While  an  analysis  will  give  the  com- 
position of  the  ash,  it  will  not  tell  under  what  trade  name  the 
material  may  have  l>een  bought. 

In  this  connection  it  is  interesting  to  note  the  following  percentages  of 
ash  in  fibrous  raw  materials  as  given  by  Wrede.  (Paper,  Jan.  31,  1912)*  (3). 

Stock 

Bleached  linen  hal  f  stuff 

Bleached  cotton   half  stuff 

Unbleached  cotton  half  stuff 

Sulphite,    unbleached    

Soda    

Adansonia   

Japanese  fibers  


Ash  % 

0.12—1.86 

0.24—0.79 

0.24—1.12 

0.48—1.25 

0.36—1.40 

5.70—7.19 

2.5 

(b~)  Qualitative  *(4,  11,  69).— To  determine  the  kind  of  load- 
ing or  coating  material  used,  it  is  necessary  to  test  the  ash  quali- 
tatively, for  which  purpose  at  least  0.2  g.  of  ash  is  desirable.  Brief- 
ly, tests  should  be  made  for  the  substances  indicated  in  table,  in 
which  are  also  given  the  fillers  that  the  presence  of  these  sub- 
stances would  indicate. 

PAPER  FILLERS  AND  THEIR  INDICATORS  *(91) 


Substance 

Calcium  sulphate   .  . 
Calcium  carbonate  . 
Barium  sulphate    .  . 
Magnesium  silicate 
Aluminum  silicate   . 


Filler  indicated 
Crown   filler 
Chalk 
Blanc  fixe 
Talc 
China  clay 


These  fillers  have  various  trade  names  and  do  not  in  all  cases 
have  definite  chemical  formulas,  but  the  presence  of  any  great 
amount  of  any  of  the  materials  in  the  first  column  would  indicate 
the  kind  of  filler  used,  and  further  confirmatory  tests  may  be  made. 

Burn  enough  paper  to  obtain  at  least  0.2  g.  ash  in  a  platinum 
or  nickel  crucible.  Separate  1/3  of  the  ash  from  the  main  portion; 
to  this  1/3  add  5  cc.  water  and  boil  until  well  extracted ;  lilter ; 
add  a  drop  of  hydrochloric  acid  to  the  filtrate  and  then  3  cc.  10 
per  cent  barium  chloride  solution.  A  white  precipitate  is  due  to 
calcium  sulphate  or  crown  filler  in  the  paper.  To  the  residue  from 
the  water  extraction  add  dilute  hydrochloric  acid.  Effervescence 
of  carbon  dioxide  gas  is  due  to  chalk  in  the  paper.  This  test  for 
chalk  may  lye  applied  directly  to  the  paper  before  ignition  if  the 
presence  of  chalk  is  suspected  at  the  start. 

To  the  2/3  portion  of  the  ash  add  1  g.  sodium  carbonate  and 
mix  well.  Fuse  the  mass  in  a  platinum  crucible  until  it  becomes 
a  clear  quiet  liquid.  Cool  and  dissolve  in  boiling  dilute  hydro- 
chloric acid.  This  solution  should  be  clear.  If  an  undissolved 
white  residue  remains,  filter  this  off.  It  is  probably  due  to 
barium.  Dip  a  clean  platinum  wire  in  this  residue  and  hold  it  in 
a  bunsen  flame.  Barium  will  give  a  characteristic  green  color. 
This  shows  the  presence  of  blanc  fixe. 

If  the  previous  hydrochloric  acid  solution  was  clear  evaporate 
nearly  to  dryness.  Dip  a  clean  platinum  wire  in  this  mass  and  test 
for  barium  as  given  above.  Then  take  up  the  mass  with  dilute 
hydrochloric  acid ;  boil ;  filter.  The  residue  is  silica  from  silicates 
in  the  filter.  A  portion  of  this  filtrate  can  be  used  as  a  confirma- 
tory test  for  sulphates.  To  the  filtrate  from  the  silica  separation 
add  ammonium  hydroxide  until  slightly  alkaline.  A  white  floccu- 


lent  precipitate  shows  the  presence  of  aluminum.  Filter  off  this 
precipitate  and  make  the  filtrate  acid  with  oxalic  acid.  Make  alka- 
line slowly  with  ammonium  hydroxide.  The  formation  of  a  white 
precipitate  shows  the  presence  of  calcium.  Filter  off  this  precipi- 
tate and  make  the  filtrate  alkaline  with  ammonium  hydroxide. 
Add  5  cc.  saturated  solution  of  sodium  acid  phosphate  and  stir 
with  a  rod.  There  will  be  a  crystalline  precipitate  formed  if 
magnesium  is  present.  It  forms  slowly  and  is  best  brought  down 
by  an  occasional  rubbing  of  the  sides  of  the  beaker  with  a  stirring 
rod. 

These  tests  indicate  the  possible  combinations  of  elements  in 
the  filler.  Where  there  are  several  names  for  one  chemical  com- 
bination— such  as  talc,  asbestine,  agaiitc,  etc. — for  various  mag- 
nesium silicates  a  microscopic  analysis  and  comparison  of  the. 
crystal  form  with  known  samples  is  necessary.  Quantities  of  al- 
uminum invariably  indicate  clay.  Silica  and  magnesium  indicate 
talcs,  agalitcs  or  asbestine  and  water-soluble  sulphates  from  filler 
point  to  calcium  sulphate. 

*(12). — If  the  paper  contains  calcium  sulphate,  the  ash  obtained 
may  consist  partly  of  calcium  sulphide,  due  to  reducing  action  of 
the  carbon  found  on  ignition,  and  the  amount  will,  therefore,  not 
represent  the  true  amount  added.  The  ash  should  be  moistened 
with  a  few  drops  of  sulphuric  acid,  and  again  ignited,  in  order  to 
reconvert  it  into  calcium  sulphate.  It  should  also  'be  borne  in 
mind  that  the  sulphate  of  lime  as  present  in  the  paper  is  combined 
with  two  atoms  of  water  (CaSO,  -j-  2H:O),  and,  therefore,  that 
every  part  of  calcium  sulphate  obtained  represents  1.26  parts  of 
pearl-hardening  actually  in  the  paper. 

(c)  Amount  of  Coating.  *(11). — Weigh  a  piece  of  the  paper 
cut  exactly  2  x  5  in.  and  place  in  a  flat  glass  dish.  The  dishes 
used  for  developing  in  photography  are  convenient  for  this  pur- 
pose. Cover  with  water  containing  1  per  cent  of  NH,OH  and  set 
aside  in  a  warm  place  (2  or  3  hrs.  is  generally  sufficient  to 
loosen  the  coating).  Remove  the  paper  to  a  large  watch  glass, 
rub  the  surface  with  a  small  camel's  hair  brush  cut  off  square, 
and  wash  the  coating  into  a  beaker.  If  the  paper  is  double-coated, 
turn  it  over  and  repeat  on  the  other  side.  Continue  the  operation 
until  all  the  coating  is  washed  into  the  beaker.  Dry  the  paper 
and  weigh  it  under  the  same  conditions  as  those  under  which  the 
original  paper  was  weighed.  The  loss  in  weight  is  the  weight  of 
coating.  Calculate  this  to  per  cent  of  the  original  sample  and  also 
figure  the  weight  of  coating  on  the  basis  of  a  ream  of  25  x  40,  500. 

•2.     Paraffin 

There  are  several  paraffin  solvents  which  may  lie  used  for  this 
determination.  Gasoline  is  easily  obtained  and  comparatively  cheap. 
It  has,  however,  the  serious  disadvantage  of  being  very  inflam- 
mable. Carbon  tetrachloride  (CC1.)  is  not  combustible.  It  is 
superior  to  chloroform,  since  the  fumes  are  not  likely  to -produce 
anesthesia.  Both  gasoline  and  carbon  tetrachloride  have  lx?en  found 
satisfactory. 

Note — Carbon  tetrachloride  cannot  be  kept  in  ordinary  "tin"  cans  on  ac- 
count of  its  actitn  on  iron. 

Enough  of  the  paper  must  be  taken  to  obtain  a  weighable 
amount  of  paraffin.  One  or  2  g.  of  paper  should  be  sufficient. 

Place  the  paper  in  a  soxhlet  or  in  an  ordinary  erlenmeyer  flask 
fitted  with  a  reflux  condenser,  cover  with  gasoline  or  carbon 
tetrachloride  and  extract  until  the  paraffin  is  all  dissolved.  If  the 
erlenmeyer  flask  be  used  it  will  probably  be  necessary  to  make  a 
second  extraction  with  a  fresh  amount  of  solvent. 

The  solution  may  then  be  evaporated  to  dryness  and  the  paraffin 
weighed.  If  the  paraffin  shows  a  tendency  to  "creep"  over  the 
edge  of  the  dish  it  may  be  easier  to  weigh  the  paper  before  and 
after  extraction  and  consider  the  loss  in  weight  as  paraffin. 

The  following  qualitative  test  for  paraffin  known  as  the  Dunlofi 


PAPER    TESTING    METHODS 


33 


method   may   be  of  value   for  determining  the  presence  of  paraffin 
in  the  presence  of  rosin : 

It  consists  in  boiling  the  sample  with  acetic  anhydride  and  ob- 
serving the  behavior  of  the  solution  on  cooling.  If  paraffin  is 
present  the  anhydride  becomes  turbid  and  the  paraffin  separates  out 
on  the  top  in  a  white  precipitate.  Less  than  1  per  cent  of  paraffin 
may  be  detected  in  this  manner.  (Allen's  Commercial  Organic 
Analysts.) 

3.     Sizing  Materials 

a.     Kosiii.—.fiiiiiniet    Method:      Alcohol-ether    Method.      *(103). 

Cut  5  g.  of  paper  into  strips  approximately  l/2  in.  wide  and 
fold  them  into  numerous  small  crosswise  folds.  Place  the 
folded  strips  in  a  soxhlet.  extractor  and  fill  with  acidulated 
alcohol.  Acidulated  alcohol  solution  is  made  by  adding  900  cc.  of 
95  per  cent  alcohol  to  95  cc.  of  distilled  water  and  5  cc.  of  glacial 
acetic  acid.  Place  the  soxhlet  flask  directly  in  the  boiling  water  of 
a  steam  bath  and  extract  by  siphoning  from  six  to  twelve  times, 
according  to  the  nature  of  the  paper.  Wash  the  alcoholic  ex- 
tract of  rosin,  which  may  contain  foreign  material,  into  a  beaker 
and  evaporate  to  a  few  cc.  on  a  steam  bath.  Cool,  take  up  in  about 
25  cc.  of  ether,  transfer  to  a  300  cc.  separatory  funnel  containing 
about  150  cc.  of  distilled  water  to  which  has  been  added  a  small 
quantity  of  sodium  chloride  to  prevent  emulsification,  shake  thor- 
oughly and  allow  to  separate.  Draw  off  the  water  into  a  second 
separatory  funnel  and  repeat  the  treatment  with  a  fresh  25  cc. 
portion  of  ether.  Combine  the  ether  extracts  which  contain  the 
rosin  and  any  other  ether-soluble  material  and  wash  twice  or  until 
the  ether  layer  is  perfectly  clear  and  the  line  between  the  ether 
and  the  water  is  sharp  and  distinct,  with  100  cc.  portions  of  dis- 
tilled water  to  remove  salts  and  foreign  matter.  Should  glue  which 
is  extracted  from  the  paper  by  alcohol  interfere  by  emulsifying 
with  the  ether,  it  may  be  readily  removed  by  adding  a  strong 
solution  of  sodium  chloride  to  the  combined  ether  extracts,  shak- 
ing thoroughly  and  drawing  it  off,  repeating  if  necessary  before 
washing  with  distilled  water.  Transfer  the  washed  ether  extract 
to  a  weighed  platinum  dish,  evaporate  to  dryness  and  dry  in  a 
water  oven  at  from  98  to  100°C.  for  exactly  one  hour,  cool  and 
weigh.  This  length  of  time  is  sufficient  to  insure  complete  drying. 
Prolonged  heating  causes  a  continual  loss  of  rosin. 

Some  objections  have  'been  made  to  portions  of  the  foregoing 
method.  It  has  been  stated  that  the  sodium  chloride  is  sufficiently 
soluble  in  the  ether  to  produce  high  results.  Some  also  prefer  to 
carry  the  evaporation  of  the  alcohol  extract  to  complete  dryness 
and  then  take  up  in  ether  and  in  water.  The  residue  as  obtained 
is  only  partially  soluble  in  ether,  but  in  case  the  entire  amount  of 
ether-soluble  material  should  not  be  secured,  after  as  much  has 
been  dissolved  by  the  ether  as  possible,  the  remainder  of  the  resi- 
due is  taken  up  in  water.  The  ether  and  water  is  then  separated 
in  a  separatory  funnel  in  the  usual  manner.  There  appears  to  'be 
no  reason  why  a  glass  dish  should  not  be  as  satisfactory  as  a 
platinum  dish.  It  is  also  asserted  that  the  extraction  may  be 
carried  out  in  an  erlenmeyer  flask  instead  of  a  soxhlet.  The  num- 
ber of  extractions  required  depend  upon  the  character  of  the  paper 
used.  In  some  individual  cases  it  has  been  found  that  a  single 
extraction  took  out  practically  all  the  rosin.  This  extraction  was 
done  on  a  hot  plate  and  the  alcohol  was  in  contact  with  the  paper 
for  about  half  an  hour.  It  is  not  known  to  what  extent  this  time 
could  be  shortened  or  in  what  per  cent  of  cases  a  single  extraction 
would  be  sufficiently  accurate. 

Note — for  extractine  rosin,  the  apparatus  shown  in  Fig.  43  will  do  the 
work  of  a  soxhlet  extractor  with  greater  convenience.  It  is  essentially  the 
same  as  the  soxhlet  in  principle,  but  can  be  set  up  very  quickly,  takes  less 
solvent,  keeps  the  crndensed  solvent  surrounded  by  hot  vapors,  occupies  less 
spaces  and  is  less  liable  to  breakage.  The  time  of  extraction  is  lessened  be- 
cause of  more  frequent  flushing  of  the  small  well  with  the  condensed  solvent. 
This  apparatus  is  listed  as  an  Undem-riter's  Extractor,  and  has  been  exten- 
sively used  in  the  extraction  of  rubber. 

QUALITATIVE  TEST  FOR   ROSIN. 
Boil  a  small  portion  of  the  paper  in  5  cc.  acetic  anhydride  in  a 


dry  test  tube.  Cool.  Add  carefully  down  the  side  of  the  test  tube 
a  small  amount  of  concentrated  sulphuric  acid.  The  development 
of  a  pink  ring  shows  the  presence  of  rosin. 

Rosin  *(3)  is  used  almost  exclusively  in  the  beater  to  impart 
waterproof  properties  to  the  paper.  There  is  no  single  test  of  a 
simple  nature  which  will  demonstrate  positively  the  presence  or 
absence  of  rosin  and  any  judgment  regarding  it  must  be  based  on 
the  indications  of  a  number  of  different  tests.  If  a  little  ether  is 
dropped  onto  a  sheet  of  paper  and  allowed  to  evaporate  there  will 
be  formed,  in  the  case  of  rosin-sized  paper,  a  ring  of  rosin  at  the 
edge  of  the  zone  where  the  ether  evaporated.  .  This  will  be  absent 
in  most  unsized  papers,  and  it  will,  of  course,  be  formed  in  any- 
paper  which  contains  any  ether  soluble  material  besides  rosin. 

Another  test  is  made  by  boiling  a  little  of  the  paper  for  a  few 

minutes    in   glacial   acetic   acid   and   pouring  the   acid   into   a    little 


FIG.  45.    ROSIN  EXTRACTION 

A  simple  apparatus  for  determining  the  rosin  content  of  paper  (American 
Writing  raper  Company,  Holyoke,  Mass.) 

distilled  water.  A  pronounced  turbidity  indicates  rosin,  but  a  slight 
opalescence  may  be  caused  by  other  soluble  substances  and  must 
be  disregarded. 

A  third  test  is  that  known  as  the  Raspail  reaction.  If  a  drop 
of  concentrated  sulphuric  acid  be  placed  on  the  paper  and  a  grain  or 
two  of  sugar  added  a  pronounced  raspberry  red -color  will  develop 
with  rosin-sized  papers,  while  with  unsized  papers  red  color  is  also 
formed  when  albuminous  materials  are  present  so  they  must  first 
be  proved  absent  before  the  test  can  be  considered  indicative  of 
rosin. 

(fe)  Glut  and  Casein. — There  appears  to  be  no  quantitative 
method  known  for  the  determination  of  these  materials  in  the 
presence  of  each  other.  Both  substances  contain  nitrogen.  If 
only  one  be  present  and  the  nitrogen  content  of  the  original  ma- 
terial as  added  to  the  paper  be  known,  then  by  means  of  the  nitro- 
gen determination  the  content  of  glue  or  casein  may  be  determined. 

QUALITATIVE  TEST  FOR  GLUE. 

Boil  a  small  portion  of  the  paper  with  10  cc.  of  water  in  a  test 
tube.  Decant  the  extract  to  another  test  tube  and  cool.  Then  add 
5  cc.  of  ammonium  molybdate  solution,  followed  by  a  few  drops 
of  nitric  acid.  The  formation  of  a  white  amorphous  precipitate 
shows  presence  of  glue. 


34 


I 'A  PER     TESTING     METHODS 


DETERMINATION   OF    NITROGEN 

Place  from  3  to  5  g.  of  the  paper  which  has  been  cut  into  small 
pieces  in  a  kjeldahl  digestion  flask,  add  ten  g.  potassium  sulphate, 
0.7  g.  of  mercury  and  25  cc.  of  concentrated  sulphuric  acid. 

The  mercury  acts  as  a  catalytic  agent  aiding  in  the  decomposi- 
tion of  the  nitrogenous  material.  The  potassium  sulphate  serves  to 
raise  the  boiling  point  of  the  sulphuric  acid.  It  is  probable  that 
sodium  sulphate  can  be  used  in  place  of  potassium  sulphate,  but  it 
is  recommended  that  15  g.  of  sodium  sulphate  crystals  be  used 
in  this  case. 

Heat  gently  at  first  to  avoid  frothing  and  finally  increase  the 
heat  as  the  digestion  proceeds.  At  the  finish  the  solution  should 
be  colorless,  or  of  a  pale  straw  color,  and  of  a  syrupy  consistence. 
At  the  completion  of  the  digestion,  which  may  require  one  and  a 
half  to  two  hours,  the  contents  of  the  flask  are  allowed  to  cool 
and  30  cc.  of  a  4  per  cent  solution  of  potassium  sulphate  arc  added. 

The  potassium  sulphate  is  necessary  to  break  up  nitrogen  com- 
pounds of  mercury.  Other  materials  than  potassium  sulphide  have 
been  used  for  this  purpose,  but  are  not  recommended. 

Before  the  distillation  can  be  made  the  mass  must  be  rendered 
alkaline.  First  dilute  with  about  200  cc.  of  distilled  water  and  then 
neutralize  by  adding  an  excess  of  saturated  solution  of  sodium 
hydroxide. 

The  volume  of  the  solution  after  the  sodium  hydroxide  has  been 
added  should  be  about  400  cc.,  therefore  the  volume  of  water  added 
must  be  calculated  so  that  just  enough  room  would  be  left  for  the 
sodium  hydroxide  solution.  Commercial  sodium  hydroxide  (95 
per  cent)  has  been  found  satisfactroy. 

There  should  be  an  excess  of  caustic  soda  equal  to  about  5  cc. 
of  a  saturated  solution.  It  is  convenient  to  add  a  few  drops  of 
methyl  orange  indicator  or  phenolphthalein  indicator  solution  to 
the  flask  before  adding  the  sodium  hydroxide.  The  solution  will 
become  yellow  or  red  respectively  when  it  becomes  alkaline. 

The  sodium  hydroxide  solution  is  carefully  poured  down  the  side 
of  the  flask  so  that  it  does  not  mix  with  the  contents.  The  flask 
is  immediately  connected  to  the  condenser  and  then  the  flask  is 
shaken  in  order  to  thoroughly  mix  the  contents. 

If  about  5  g.  of  granulated  zinc  or  a  few  small  pieces  of  pumice 
.stone  are  added  to  this  flask  just  before  the  sodium  hydroxide,  they 
will  help  to  prevent  bumping. 

The  distillate  is  caught  in  a  flask  containing  a  known  amount 
of  standard  acid  diluted  to  a  volume  of  -100  cc.  with  distilled 
water.  (The  equivalent  of  30  cc.  n/10  normal  acid  should  be 
ample.)  A  few  drops  of  indicator  should  be  added  to  this  solution. 
Sodium  alizarin  sulphonate  and  methyl  red  have  been  recom- 
mended as  indicators.  The  end  of  the  condenser  tube  should  dip 
beneath  the  surface  of  the  acid.  The  distillation  should  continue 
for  45  min.  and  the  distillate  should  equal  200  cc.  Titrate  with 
n/10  normal  alkali. 

This  same  operation  of  distillation  should  be  carried  out,  using 
only  the  chemicals  involved  in  order  to  have  a  check  on  their 
purity.  This  is  known  as  the  "blank." 

.Subtract  the  number  of  cc.  of  n/10  normal  alkali  required  to 
neutralize  the  distillate,  from  the  number  of  cc.  required  by  the 
Wank.  This  difference  is  the  number  cc.  of  n/10  normal  alkali 
equivalent  to  ammonia. 

No.  cc.X0.014=g.  nitrogen. 

The  following  factors  should  be  used  on  unknown  samples : 
For  casein  use  the  factor  6.3  and  for  glue  use  the  factor  5.6.  In 
all  cases  this  factor  should  be  determined  wherever  possible,  as 
those  values  will  vary,  depending  on  the  grade  of  material  used. 

Note — Copper  sulphate,  weight  for  weight,  can  be  substituted  for  the 
mercury  as  a  catalytic  agent  in  this  determination;  it  serves  as  an  indicator 
for  alkalinity  by  turning  a  characteristic  blue  when  the  solution  is  made 
alkaline  previous  to  distillation.  Small  glass  beads  can  be  effectively  sub- 
stituted for  granulated  zinc  to  prevent  bumping  in  the  distilling  flask. 


Casein  *(3)  may  be  detected  in  paper  by  moistening  the  sample 
with  Millon's  reagent  and  wanning  gently  either  over  a  flame  or 
over  an  open  steam  bath.  If  casein  is  present  a  brick-red  color  _ 
will  develop.  In  the  case  of  coated  paper  in  which  much  satin 
white  is  used,  the  alkali  present  determines  the  formation  of  a 
yellow  color.  In  this  case  proof  may  be  obtained  by  moistening 
the  paper  first  with  dilute  nitric  acid,  to  neutralize  the  alkali,  and 
then  applying  the  Millon's  reagent  as  before;  tested  in  this  way 
satin  white  coated  paper  will  give  the  usual  red  color.  Casein 
may  also  be  detected  by  boiling  the  paper  with  water  and  a  few 
drops  of  ammonia,  filtering  and  adding  to  the  filtrate  dilute  acetic 
acid  very  gradually.  Casein  will  precipitate  when  the  solution 
becomes  very  faintly  acid,  but  it  may  redissolve  on  adding  a  con- 
siderable excess.  This  test  is  also  given,  though  usually  less 
strongly,  by  rosin,  so  the  precipitate  should  be  tested  with  Millon's 
reagent  to  confirm  the  presensc  of  casein.  Casein  is  seldom  used 
except  in  the  coating;  cases  of  surface  sizing  or  of  its  use  in  the 
beaters  are  very  rare. 

Glue  *(3)  is  sometimes  used  as  an  adhesive  in  coating  papers 
and  in  rare  instances  in  the  beaters :  the  better  grades  known  as 
gelatines  are  used  in  surface  sizing.  If  glue  is  present  alone  it 
may  'be  detected  by  boiling  the  sample  of  paper  in  water,  filtering 
if  necessary,  and  adding  a  little  dilute  tannic  acid  solution ;  a 
grayish,  flocculent  precipitate  indicates  glue.  Casein  is  also  pre- 
cipitated by  tannic  acid  and  the  presence  of  starch  prevents  the 
precipitation  of  glue  so  that  when  either  casein  or  starch  is  present 
there  is  apparently  no  means  of  proving  the  presence  or  absence 
of  glue. 

r.  Starch:  Procedure  for  Analysis. — The  paper  to  be  analy/.ecl 
is  tested  with  the  usual  iodine  reagent.  If  but  a  trace  of  starch 
is  present,  no  acetic  acid  is  required  in  extraction.  A  5-g.  sample 
is  cut  into  small  pieces  and  placed  in  a  500-cc.  round-bottom  nask. 
200  cc.  of  water  is  added,  and  5  cc.  glacial  acetic  acid  is  run  in. 
making  a  2'/2  per  cent  solution.  The  flask  is  connected  with  a 
reflux  condenser  by  means  of  a  clean  rubber  stopper  and  the 
contents  boiled  vigorously  for  I1/;  hrs.  The  extract  is  decanted 
through  a  Biichner  funnel  equipped  for  suction  filtration  and  the 
pulp  washed  with  about  50  cc.  of  hot  water.  To  the  filtrate  is 
added  15  cc.  of  HC1  (37  per  cent)  and  boiling  continued  for  30 
min..  the  volume  of  the  solution  being  permitted  to  decrease  by 
evaporation  to  al>out  200  cc.  The  hot  acid  solution  is  neutralized 
by  the  addition  of  solid  sodium  carbonate  until  effervescence  ceases 
and  the  volume  is  determined.  This  solution  is  titrated  into  a 
measured  quantity  of  Fehling's  solution  (2  to  10  cc.,  according  to 
the  amount  of  starch  present).  After  each  addition  of  sugar 
solution  the  mixture  is  heated  to  the  boiling-point' and  maintained 
at  that  temperature  for  1  min.  The  reaction  mixture  may  be 
diluted  if  this  is  considered  desirable.  The  end-point  is  determined 
on  a  spot  plate  with  a  potassium  ferrocyanide-acetic  acid  solution 
and  is  that  point  at  which  no  immediate  color  is  produced  on  tin- 
plate  :  it  may  be  determined  to  within  V*  to  1  cc.  of  sugar  solution, 
depending  on  the  volume  of  solution  employed.  It  was  found  that 
the  potassium  ferrocyanide  became  colored  when  allowed  to  remain 
a  number  of  days  with  the  acetic  acid,  and  that  a  sharper  and  more 
distinct  end-point  can  be  obtained  if  the  acid  is  added  separately  to 
the  spot  plate  when  the  test  is  to  be  made.  One  drop  of  each 
solution  is  used  for  a  test. 

QUANTITATIVE  ANALYSIS  FOR  STARCH*   (120) 
Method  of  Kannn  ami   I'norlices. 

PREPARATION  OF  RKAGK\TS — The  usual  Fehling's  solution  is  em- 
ployed. 

Solution  A — 69,3  g.  of  crystallized  copper  sulphate  arc  dissolved  in  water 
and  the  solution  diluted  to  1,000  cc. 

Solution  B — 346  g.  of  Rochelle  salt  and  120  g.  of  si  ilium  hydroxide  are 
dissolved  in  water  and  the  solution  also  diluted  to  1,000  cc. 

Sofutions  A  and  fi  are  kept  separate  and  equal  volumes  mixed 
when  ready  to  be  used.  In  a  given  experiment,  where  it  is  reported 


PAPER    TESTING    METHODS 


35 


that  10  cc.  of  Fehling's  solution  is  used,  it  is  understood  that  5  cc. 
of  solution  .-I  is  added  to  5  cc.  of  solution  B.  According  to  the 
literature,  10  cc.  of  such  a  solution  should  be  equivalent  to  0.05 
grains  of  dextrose  when  an  analysis  is  run  in  a  specified  empirical 
manner.  It  is  found  more  convenient  to  standardize  the  solution 
with  a  known  quantity  of  starch,  the  latter  being  hydrolyzed  and 
titrated  under  the  same  conditions  used  later  for  the  hydrolysis 
and  titration  of  starch  in  paper.  The  advantage  is  obvious. 

Potassium  fcrrocyanidc  solution.  A  10  per  cent  solution  of 
K,Fe(CN)«3Ht;O  is  used. 

Acetic  acid  solution.  A  50  per  cent  solution  of  acetic  acid  is 
found  convenient. 

METHOD  OF  CALCULATION  OF  RESULTS 

It  has  already  been  suggested  that  Fehling's  solution  be  stand- 
ardized against  one  of  the  ordinary  starches  used  in  paper  manu- 
facture. Such  a  procedure  is  justified  by  the  close  agreement  in 
the  reducing  values  of  corn-starch,  Hercules  gum,  feculose  and 
dextrin. 

Example — A  sample  of  corn-starch  was  dried  at  105°  C.  for  3 
hrs.  A  .05-g.  portion  was  then  weighed  out  and  hydrolyx.ed 
with  about  190  cc.  of  a  4  per  cent  HC1  solution  during  a  period 
of  30  min.  After  neutralization  with  solid  sodium  carbonate, 
the  final  volume  was  adjusted  to  200  cc.,  and  the  solution  titrated 
against  10  cc.  of  Fehling's  solution ;  20  cc.  of  sugar  solution  were 
required  and  10  cc.  of  Fehling's  solution  are  therefore  equivalent 
to  20/^00  X  O.SO  —  0.050  g.  starch. 

In  an  analysis  of  a  5-g.  sample  of  paper  the  volume  of  the  final 
hydrolysis  mixture  was  217  cc.  Of  the  latter  solution  39  cc.  were 
required  for  reaction  with  10  cc.  of  Fehling's  solution.  The  per 
cent  of  starch  in  the  sample  of  paper  is  therefore : 

217  Yalm-  of  Fehlins's  solution   in  g.  of  starch    X    100 

—  =  5.5  per  cent 
39  Wt.  of  sample  of  paper 

Since,  however,  a  5-g.  sample  of  paper  is  used,  and  since  our 
Fehling's  solution  is  equivalent  to  0.05  g.  starch  to  10  cc.  of  solu- 
tion, the  calculation  is  simplified  thus : 


217 
39 


=  5.5  p«r  cent  starch. 


Mention  might  be  made  of  the  polarimetric  method  of  Dr.  C.  E. 
G.  Porst  and  H.  A.  Crown.  See  Journal  of  Industrial  and  Engi- 
neering Chemistry,  vol.  5,  No.  4,  April,  1913. 

QUALITATIVE  TEST  TO  INDICATE  ITS   PRESENCE  IN   PAPER 

Make  a  dilute  solution  of  iodine  in  potassium  iodide  by  adding 
a  small  amount  of  water  to  a  mixture  of  three  or  four  crystals  of 
iodine  and  1  g.  of  potassium  iodide,  stirring  until  the  iodine  is 
completely  dissolved,  and  then  diluting  the  solution  with  pure 
water  until  a  pale  straw-yellow  color  is  obtained.  Add  a  drop  of 
this  solution  to  the  paper  under  examination,  a  blue  color  indicates 
the  probable  presence  of  starch.  If  this  blue  coloration  is  obtained 
it  is  well  to  confirm  the  test  by  boiling  the  paper  with  water  and 
testing  the  water  extract  with  the  iodine  solution,  because  cellu- 
lose in  the  presence  of  water  when  subjected  to  certain  mechanical 
processes  gives  rise  to  modifications  known  as  hydrocelluloses. 
These  hydrocelluloses  are  not  soluble  to  any  great  extent  in  boiling 
water,  but  they  will  give  rise  to  a  blue  coloration  when  brought 
into  direct  contact  with  the  iodine  solution. 

An  alternate  procedure  is  as  follows:  The  universal  test  for 
starch  *(3)  is  to  apply  a  dilute  iodine  solution  to  the  paper  when 
a  blue  to  violet  color  will  appear  if  starch  is  present.  It  is  well 
to  confirm  this  test  by  boiling  some  of  the  paper  with  a  little  water, 
filtering  and  testing  the  filtrate,  after  cooling,  with  a  few  drops 
of  iodine  solution.  This  is  necessary  because  hydrocelluloses,  which 
are  only  slightly  soluble  in  boiling  water,  also  give  a  blue  color 
when  brought  into  direct  contact  with  iodine  solution.  Micro- 
scopic examination  will  show  whether  the  starch  granules  have 


been  burst  by  boiling  or  whether  the  starch  was  used  without 
cooking.  If  the  paper  to  be  tested  is  torn  so  that  it  splits  on  the 
edge  before  being  moistened  with  the  iodine  solution  it  is  generally 
possible  to  tell  whether  it  is  surface  sized  or  not.  If  it  is  surface 
sized  only,  the  interior  of  the  sheet  will  remain  white  while  the 
surface  will  turn  blue ;  if,  however,  considerable  starch  was  used 
in  the  beater,  this  is  in  part  cooked  and  drawn  to  the  surface  by 
the  heat  of  the  driers  so  that  the  paper  has  the  appearance  of  being 
surface  sized  when  in  reality  it  was  not.  Microscopic  examina- 
tion of  the  papers  after  treating  with  iodine  will  sometimes  enable 
an  opinion  to  be  formed  though  it  is  seldom  possible  to  prove 
positively  in  such  a  case  whether  the  paper  is  surface  sized  or  not. 
d.  Dextrine  in  Presence  of  Beater  Starch.  Method  of  Kamm 
and  Tendick.  *(119). — The  procedure  adopted  consists  in  the  re- 
moval of  the  surface  sizing  by  a  45-min.  leaching  of  the  sample 
of  paper  with  water  at  a  temperature  of  60°  C.  For  a  5-g.  sample 
200  cc.  of  water  is  used.  The  extra  is  removed  by  suction  filtra- 
tion and  the  soluble  carbohydrate  material  hydrolyzed  and  estimated 
according  to  the  procedure  already  described  in  detail.  See  Method 
for  quantitative  determination  of  starch.  The  starch  remaining  in 
the  paper  may  then  be  isolated  by  the  dilute  acetic  acid  extraction 
method  recommended  in  the  article  on  starch  determination. 

4.     Chlorine 

The  determination  of  free  chlorine  in  paper  is  carried  on  in  a 
manner  similar  to  that  used  in  testing  half-stuff;  namely,  take  a 
small  mass  of  the  stuff  to  IK-  tested,  from  the  beater,  press  it  with 
the  hand  and  test  with  a  few  drops  of  potassium  iodide  starch 
solution.  If  free  chlorine  is  present  the  characteristic  blue  color 
will  be  developed. 

For  the  testing  of  finished  paper  the  determination  is  best  carried 
out  as  follows.  Cut  the  paper  into  small  pieces,  moisten  with  dis- 
tilled water,  and  test  with  starch  iodide  paper ;  this  is  best  done 
on  a  glass  plate. 

Instead  of  starch  iodide  paper  one  may  mix  a  small  piece  of 
starch  to  a  paste  with  cold  water,  and  mix  it  with  a  solution  of 
potassium  iodide. 

5.     Sulphur  *(127) 

The  apparatus  consists  of  a  500  cc.  round  bottom  flask  with  a 
neck  about  2  in.  long  and  1  in.  in  diameter.  The  mouth  of  this 
neck  is  ground  to  a  flat  surface  and  on  this  is  placed  a  glass 
tube  about  4  in.  long  and  1  in.  in  diameter,  the  lower  end  of 
which  is  also  ground  flat  to  fit  tightly  upon  the  upper  surface  of 
the  neck  of  the  flask.  The  whole  is  so  arranged  that  after  placing 
a  piece  of  filter  paper  between  the  two  ground  surfaces,  the  tube 
and  flask  can  be  securely  clamped  together  so  that  all  gas  gener- 
ated in  the  flask  must  pass  through  the  filter  paper  and  then  up 
through  the  superimposed  glass  tube. 

The  procedure  for  the  testing  of  tissue  papers  is  as  follows :  A 
sample  of  25  sq.  in.  is  taken  and  its  weight  determined.  It  is 
then  shaken  up  in  a  wide  mouth,  glass-stoppered  bottle  with  10 
cc.  of  distilled  water ;  when  partial  disintegration  has  taken  place, 
another  10  cc.  of  water  is  added  and  the  shaking  continued  until 
the  paper  has  been  completely  reduced  to  pulp.  The  larger  part 
of  the  pulped  mass  is  now  transferred  to  the  flask  described  above, 
and  the  residue  which  is  left  in  the  bottle  is  rinsed  into  the  flask 
with  a  mixture  of  10  cc.  of  water. 

Prepare  turnings  from  the  highest  grade,  pure  stick  zinc,  which 
must  be  free  from  sulphur  and  arsenic.  Treat  1  g.  of  these 
turnings  with  10  cc.  of  a  dilute  solution  of  copper  sulphate  con- 
taining about  0.002  g.  actual  copper.  After  a  few  minutes  all  the 
copper  will  have  deposited  and  the  turnings  are  then  thoroughly 
washed  to  remove  every  trace  of  zinc  sulphate. 

The  turnings  are  added  to  the  flask  and  a  wad  of  cotton  inserted 
in  its  neck.  Between  the  two  ground  glass  surfaces  is  then  clamped 
a  piece  of  filter  paper  about  2  in.  square  which  has  been  per- 
forated with  small  pin  holes  about  Hi  in.  apart  and  which  just 


36 


PAPER    TESTING     METHODS 


before  use  is  moistened  with  several  drops  of  lead  acetate  solution. 
Finally  a  loose  wad  of  cotton  is  placed  in  the  tube  above  the  paper. 

The  flask  is  placed  on  the  steam  bath  and  allowed  to  stay,  with 
occasional  shakings,  for  an  hour.  The  filter  paper  is  then  removed 
from  the  neck  of  the  flask  and  air  dried.  It  is  best  compared  with 
the  standard  test  pieces  by  placing  them  side  by  side  on  a  piece  of 
white  paper  and  covering  them  with  a  thin  piece  of  clear,  white 
glass.  The  standard  test  pieces  are  prepared  by  using  sulphur- 
free  cotton  in  the  flask  instead  of  the  disintegrated  paper  and  adding 
to  this  definite  volumes  of  a  very  weak  solution  of  sodium  thiosul- 
phate  whose  strength  is  accurately  known.  The  sulphur-free  cotton 
is  prepared  .by  boiling  absorbent  cotton  in  weak  caustic  soda  solu- 
tion and  washing  thoroughly  with  distilled  water. 

The  sensitiveness  of  this  test  is  such  that  the  presence  of  0.000001 
g.  of  sulphur  in  the  flask  will  give  a  distinct  color  on  the  lead 
acetate  paper.  From  tests  of  a  considerable  number  of  papers 
which  have  been  found  satisfactory  in  actual  practice  it  has  been 
proved  that  tissue  paper  is  safe  for  wrapping  silverware  if  it  does 
not  contain  more  than  O.C00002  g.  of  sulphur  per  25  sq.  in.  of 
paper  (atout  0.25  g.)  ' 

6.     Coloring  Matter  *(28) 

Smalts,  existing  as  it  does  in  high-class  papers,  usually  without 
admixture  with  loading  materials,  can  be  estimated  with  sufficient 
accuracy  by  incinerating  the  paper,  weighing  the  ash,  and  making  a 
correction  for  the  small  proportion  of  the  latter  due  to  the  fiber, 
etc.  This  proportion  does  not  usually  exceed  2  per  cent. 

The  ultramarines  are  of  variable  and  even  doubtful  composition, 
and  are,  therefore,  best  estimated  by  comparing  the  depth  of  color 
of  the  ash  with  that  of  standard  mixtures  of  the  pigment  with 
known  proportions  of  china  clay. 

Chrome  yellow,  crant/c,  etc.,  also  of  variable  composition,  may 
be  determined,  if  necessary,  by  estimating  the  lead  and  chromium 
separately,  and  calculating  the  results  to  the  nearest  indicated  com- 
position. It  is  scarcely  necessary  here  to  describe  the  full  gravi- 
metric process  as  it  is  likely  to  be  but  rarely  required.  It  will  be 
sufficient  to  say  that  the  lead  is  precipitated  and  estimated  as  the 
sulphate,  and  the  chromium  as  chromic  oxide. 

Prussian  blue  may  be  determined  approximately  by  estimating 
the  iron  by '  igniting  the  paper,  fusing  the  ash  with  sodium  car- 
bonate, treating  the  fused  product  with  hot  water,  filtering,  and 
boiling  the  residue  with  dilute  hydrochloric  acid  and  a  drop  or 
two  of  nitric  acid.  The  solution  is  then  again  filtered,  and  the  iron 
and  alumina  precipitated  with  ammonia  in  the  presence  of  a  little 
ammonium  chloride.  The  precipitate  of  iron  and  aluminum  hydrates 
is  washed,  filtered  off,  and  digested  with  excess  of  caustic  soda, 
then  filtered  ag'ain  and  carefully  washed.  The  residue,  which  con- 
sists entirely  of  iron,  is  washed,  dried,  ignited,  and  weighed  as  the 
oxide.  This  process  also  serves  for  the  estimation  of  all  other  iron 
pigments  except  the  natural  figments,  ochres,  etc. 

7.     Tests  for  Special  Materials  *(28) 

Oils  and  fats  can  be  estimated  by  extracting  with  ether,  evaporat- 
ing the  solvent,  and  weighing  the  residue. 

Paraffin -ttw.r — Similar  to  the  above,  using  benzin  or  petroleum 
spirit. 

Salicylic  Acid — This  substance  is  used  as  a  preservative  in  papers 
required  for  wrapping  foodstuffs.  It  is  extractable  with  petroleum 
ether,  and  may  be  estimated  in  the  solution  by  diluting  the  latter 
with  an  equal  volume  of  95  per  cent  alcohol  and  titrating  with 
n/10  normal  alkali,  using  phenolphthalein  as  indicator.  Each  cc. 
of  n/10  normal  caustic  soda  is  equivalent  to  .0138  g.  of  salicylic 
acid. 

Carbolic  Acid — The  estimation  of  carbolic  acid  in  carbolized 
wrapping  paper  is  frequently  required.  Commercial  carbolic  acid 
consists  chiefly  of  cresylic  acid  with  higher  phenols,  but  little  real 


phenol  being  usually  present.  Since,  however,  cresol  is  probably 
as  efficient  an  antiseptic  and  insecticide  for  ordinary  purposes  as 
phenol,  the  absence  of  the  latter  body  is  of  little  importance.  Car- 
bolic acid  may  contain  tar  oils,  which  are,  however,  quite  inert. 
Naphthalene  is  also  liable  to  be  present. 

For  the  estimation  of  commercial  carbolic  acid  the  bromine- 
absorption  method  in  use  for  the  determination  of  phenol  is  value- 
less. The  writer  has  found  the  following  method,  which  is  based 
on  a  process  originally  described  by  Muter,  quite  satisfactory: 

From  10  to  20  g.  of  paper  (according  to  the  probable  proportion 
of  acid  present)  are  cut  into  pieces  and  extracted  with  a  sufficient 
quantity  of  alcohol  (95  per  cent)  in  a  soxhlet.  The  extract  is 
transferred  to  a  basin,  mixed  with  about  half  its  volume  of  a  10 
per  cent  solution  of  caustic  soda,  and  the  mixed  liquids  evaporated 
in  the  water  bath  to  small  bulk.  Tar  oils  and  naphthalene,  if 
present,  here  separate  out  and  may  be  removed  by  filtration.  The 
liquid  is  now  transferred  to  a  separating  funnel  and  hydrochloric 
acid  added  cautiously  and  with  gentle  shaking  until  the  liquid 
shows'  an  acid  reaction.  Means  should  be  taken  to  prevent  the 
mixture  becoming  too  hot  during  the  process.  A  little  brine  is  now 
added.  The  liberated  tar  acids  rise  to  the  surface  of  the  liquid 
which  also  becomes  milky  from  the  precipitation  of  rosin.  The 
whole  is  now  set  on  one  side  for  a  short  time  to  complete  the 
separation  of  the  layer  of  tar  acids,  after  which  the  resinous  liquid 
is  drawn  off  as  completely  as  possible.  The  residue  of  oil  is  shaken 
up  with  ether  or  petroleum  spirit,  transferred  to  the  weighed  flask, 
the -solvent  evaporated  off,  and  the  residue  weighed. 

8.     Free  Acid  in  Paper 

Weigh  10  grams  of  the  paper  to  lie  tested,  tear  into  small  pieces, 
place  in  a  250  cc.  porcelain  casserole,  and  cover  with  a  small  amount 
of  distilled  water.  Heat  gently  for  an  hour  over  water  bath  or 
electric  hot  plate.  Pour  off  water  and  wash  with  small  quantities 
of  distilled  water,  adding  it  to  water  extract. 

Another  casserole  is  filled  with  an  equal  amount  of  distilled 
water,  to  which  is  added  two  drops  of  a  methyl  orange  solution 
(0.1  per  cent  solution  in  water).  To  the  former  is  then  added  tenth 
normal  standard  solution  of  caustic  soda  until  the  color  matches 
the  sample.  The  acidity  is  then  expressed  in  terms  of  sulphuric 
acid  (rLSO,). 

An  alternate  method  is  as  follows :  Take'  a  piece  of  the  paper 
six  inches  square,  place  in  a  saucer,  and  pour  over  it  distilled 
water,  and  work  about  with  a  glass  rod  for  5  or  6  min.  Now 
take  a  blue  litmus  paper  or  a  little  tincture  of  litmus  and  test 
the  extract,  when  if  either  turn  red  it  shows  the  presence  of  acid. 
Divide  the  extract  into  two  parts ;  to  one  add  a  few  drops  of 
nitric  acid,  then  nitrate  of  silver  solution,  when  if  a  white  curdy 
precipitate  is  formed,  it  proves  the  presence  of  hydrochloric  acid 
or  chlorides.  To  the  second  portion  add  a  few  drops  of  hydro- 
chloric acid,  heat  to  boiling  in  a  test  tube,  and  add  a  solution  of 
barium  chloride;  a  white  precipitate  indicates  the  presence  of  sul- 
phuric acid  or  sulphates. 

9.     Tarnishing  Test  *(11) 

A  paper  which  is  to  be  used  for  wrapping  silverware  should  be 
essentially  free  from  active  sulphur  compounds.  The  method  of 
testing  so  called  "anti-tarnish"  paper  consists,  in  general,  of  com- 
paring the  sample  to  be  tested  with  special  papers  impregnated 
with  0.001  per  cent  and  0.0001  per  cent  Na:S  solutions,  the  sul- 
phide test  in  each  case  being  made  under  prescribed  conditions  by 
a  hydrogen  evolution  method  and  lead  acetate  paper. 

Preparation  of  Special  Impregnated  Papers. — Make  the  special 
papers  from  10  cm.  best  white  filter  paper,  each  of  which  weighs 
approximately  0.6  gram.  Prepare  the  following  solutions  : 

a.  Dissolve  3  grams  of  fresh  sodium  sulphide  crystals  in  100  cc. 
of  distilled  water.  (3  g.  of  Na=S9H...O  are  equivalent  to  1  g  of 
Na^S.) 


PAPER     TESTING     METHODS 


37 


b.  Dilute    1   cc.   of   solution    (a)    to   1   liter  to  make   a  0.001    per 
cent  'Na=S  solution. 

c.  Dilute  10  cc.  of  solution   (b)   to  100  cc.  to  make  a  0.0001  per 
cent  Xa»S   solution. 

Saturate   the   filter    paper   in   solution    (b)    and    (c)    and   dry   in 
air.     Considerable  quantities   of  these  papers  may  be  made  at  one 
time  and  stored  in  separate,  tightly  stoppered  bottles  labeled : 
"0.001     per   cent   Na,S   paper   for  tarnishing  test." 
"0.0001   per  cent   Na2S  paper   for  tarnishing  test." 

The  papers  may  also  be  torn  into  four  equal  segments,  each 
segment  (0.1S  gram)  being  sufficient  for  one  test. 

Materials  Required—  ( 1 )  Four  500-cc.  flat  bottom  flasks,  approxi- 
mately 7  inches  high;  (2)  Granulated  zinc  (arsenic  free);  (3)  15 
per  cent  HC1  solution;  (4)  Lead  acetate  test  paper,  moistened;  (5) 
Absorbent  cotton. 

Method — Into  each  flask  put  2  grams  of  granulated  zinc  and 
0.15  gram  of  paper  torn  into  small  pieces.  The  four  flasks  are  for 
the  following  papers:  (1)  Sample;  (2)  Pure  filter  paper  (for  a 
"blank");  (3)  0.001  per  cent  Na2S  paper;  and  (4)  0.0001  per 
cent  Na,S  paper. 

Add  to  each  flash  25  cc.  of  15  per  cent  HC1  (free  from  As). 
Into  the  neck  of  the  flask  insert  a  loose  plug  of  cotton  to  a  depth 
of  about  1.5  in.  Above  the  cotton  place  a  piece  of  moistened 
lead  acetate  test  paper  about  one  inch  square,  and  cover  this  loosely 
with  a  plug  of  cotton.  Set  the  four  flasks  in  a  pan. or  tub  contain- 
ing water  at  room  temperature  to  a  depth  of  025-0.50  inch,  or  in 
order  to  prevent  any  considerable  rise  of  temperature  of  the  con- 
tents of  the  flask.  The  liberated  hydrogen  will  carry  any  H.S 
evolved  up  to  the  lead  acetate  paper,  which  will  darken.  Examine 
the  four  lead  acetate  papers  at  the  end  of  30,  60  and  90  minutes 
and  record  their  comparative  appearances. 

^Interpretation  of  Results — It  has  been  found  that  the  O.C01  per 
cent  Na«S  paper  causes  some  tarnishing  when  held  in  contact  with 
a  polished  10  cent  piece  for  five  weeks.  Commercial  papers  known 
to  have  caused  tarnishing  of  polished  metal  goods  have  been  found 
to  lie  more  reactive  under  this  test  than  the  0.001  per  cent  Na2S 
paper.  Therefore,  a  paper  to  be  acceptable  should  show  up  as  well 
as  the  0.0001  per  cent  Na.S  paper  (which  should  show  slight 
discoloration  in  about  sixty  minutes).  A  paper  between  0.0001  per 
cent  and  0.031  per  cent  Na^.S  papers  is  dangerous ;  while  those 
that  are  inferior  to  0.001  per  cent  Na,S  paper  should  be  unques- 
tionably rejected. 

In  reporting,  a  paper  superior  to  0.0001  per  cent  Na2S  paper 
'honld  be  classed  as  "safe";  those  between  0.0001  -per  cent  and 


0.001   per  cent  Na.S  as  "questionable"  ;  and  those  inferior  to  0.001 
•per  cent   Na2S  as  "unsafe." 

Note — *The  practical  use  of  paper  for  wrapping  polished  metal  seems  to  in- 
dicate that  sulphur  in  forms  other  than  sodium  sulphide  will  produce  a  tarnish- 
ing effect.  This  subject  should  be  investigated  before  the  method  is  adopted 
generally. 

V.     INTERPRETATION   OF  DATA 

The  technique  of  paper  testing  has  developed  in  no  orderly  or 
systematic  manner  and,  in  nearly  all  cases  where  paper  is  being 
tested,  the  methods  are  used  chiefly  for  mill  control  purposes. 
In  sucli  cases,  comparative  results  only  are  necessary  and  few 
attempts  have  been  made  to  interpret  the  data  obtained  in  any 
fundamental  units.  Little  attention  has  been  given  the  calibration 
of  testing  instruments  or  the  experimental  error  of  the  methods. 
Provision  for  the  proper  error  of  sampling  and  testing  is  generally 
overlooked  and  considerable  friction  has  at  times  developed  for 
these  reasons. 

1.     Relation  of  Various  Tests 

Some  attempts  have  been  made  to  draw  a  relation  between  some 
of  the  physical  qualities  of  paper,  with  especial  reference  to  burst- 
ing, folding,  tearing,  anil  breaking  strength.  Although  there  is  a 
wealth  of  such  data  available,  both  published  and  in  laboratory 
files,  the  only  conclusions  so  far  reached  are  entirely  negative. 
In  a  given  paper,  it  is  quits  possible  to  have  a  strong  bursting 
strength  but  a  weak  tearing  and  folding  strength  and  vice  versa. 
It  is  interesting  to  note,  however,  that  both  the  bursting  and  break- 
ing strength  are  similarly  affected  by  relative  humidity,  i.  e.,  a 
maximum  strength  occurs  at  about  35  per  cent  relative  humidity. 
The  amount  of  rosin,  glue  or  starch  present  in  a  paper  does  not 
seem  to  have  any  relation  to  sizing  quality,  except  in  a  very  general 
way.  It  is  recommended  that  this  question  of  the  relation  of 
various  tests  be  studied. 

2.     Quality  Indicated  by  Tests 

It  is  quite  general  practice  to  make  certain  tests  on  paper 
whether  or  not  the  test  indicates  the  quality  in  question.  This  has 
been  due  to  lack  of  test  methods  to  some  extent  but  discrimifiation 
should  be  exercised  in  the  choice  of  the  proper  test.  Folding 
endurance  seems  to  be  the  best  method  of  determining  the  durability 
and  probable  life  of  a  paper,  while  the  bursting  strength  is  so 
affected  by  various  factors  that  the  data  obtained  with  it  are  often 
misleading.  It  is  recommended  that  data  be  collected  and  sug- 
gestions made  as  to  the  proper  tests  for  various  kinds  of  paper. 


38 


PAPER    TESTING     METHODS 


VI.     BIBLIOGRAPHY 


9. 
10. 
11. 
12. 


13. 

14. 

15. 
16. 

17. 
18. 
19. 

20. 

21. 
22. 
23. 
24. 
25. 
26. 
27. 

28. 
29. 

30. 

31. 

32. 
33. 

34. 
35. 
36. 

37. 

38. 
39 

40. 
41. 
42. 


partial  list  of  reference  books  and  articles  in  periodicals — 
1.     Books 

The  Chemistry    of   Paper    Making,    by    R.    B.    Griffin    and    A.    D.    Little. 

Chap.  9,  pp.  400-451. 

Allen's  Commercial   Organic  Chemistry.     Vol.   1,  pp.   465-480. 
Chemistry    of    Pulp    &    Paper    Making,    by    Edwin    Sutermeister.     Chap. 

15,  pp.  386-428. 

Elementary  Manual  of  Paper  Technology,  by  R.   W.   Sindall.     Chaps.  9, 

10,  11.   12,  pp.   107-213. 

Engineering  Chemistry,  by  T.  B.  Stillman.     Fifth  edition,  pp.  561-568. 
Ilandbuch   der   Papierkunde   (Hand-book  of   paper   technology),   by    Paul 

Klemm,  pp.  248-327. 
Modern    Pulp    and    Paper    Making,    by    G.    S.    Witham,    Sr.     Chap.    17, 

pp.   462-500. 

Paper  and  Its  Constituents,  by  H.  A.  Bromley.     Part  III,  pp.  141-212. 
Paper,  Its  History,  Source  and  Manufacture,  by  H'.  A.  Maddox. 
Papier  priifung  (Paper  Testing),  by  Wilhelm  Herzberg. 
Technical  Methods  of  Analysis,  by  R.  C.  Griffin,  pp.  337-363. 
A  Text  Book  of  Paper-Making,  by  C.  F.  Cress  and  E.  J.  Sevan.     Chap. 

14,  pp.  371-402. 

2.     Articles 

Absorbency  of    Paper,   by   E.   O.    Reed.     Paper,   Vol.    21,   No.    19,   p.    14. 

J'an.    16,    1918;    Jour.    Ind.    &•    Engr.    Chan.,    Vol.    10,    p.    44,    Jan. 

1918 
Absorption    Power    of    Paper    Testing.     Paper,    Vol.    29,    No.    22,    p.    12, 

Feb.   1,  1922. 

Alum  in  Paper,  Test  for.     World's  Paper  Trade  Review,  Vol.  75,  p.  12. 
Animal    Size   in    Paper.     Pafer   Makers'   Monthly  Jour.,   Nov.   15,    1919; 

Paper,  Vol.  25,  p.  622   (1919). 
Asbestos    Paper,   Estimation    of.     Pafer,   Vol.    23,    folio   p.    117,    Oct.    9, 

1918. 
Ash   Content  of   Paper,   by    Hans   Wrede.     Paper,   Vol.   6,   No.   7,   p.    13, 

Jan.  31,  1912. 
Ash  Tests  and  Their  Significance,  by  F.   E.  Plumstead,  Pulp  and  Paper 

Magazine   of  Canada,   Vol.    14,   No.   2,   p.   31,  Jan.   15,    1916,  Paper, 

Vol.   17,  No.  20,  p.  16,  Jan.  26,  1916. 
Bag  Paper  Testing  Lime  and  Cement,  by  P.   L.  Houston  Tech.  Papers 

No.   187,  Bureau  of  Standards;  Pulp  cr  Paper  Magazine  of  Canada, 

Vol.  18,  p.  947,  Sept.  9,  1920;  Paper,  Vol.  27,  p.  15,  Sept.  22,  1920. 
Balance  Pocket  Quadrant  Demy.     Paper  Makers'  Monthly  Journal,   Vol. 

59,  p.  3. 
Blue  and  Brown  Print  Paper,  by  F.  P.  Veitch,  C.  F.  Sammet  and  E.  O. 

Reed,  Jovr.  Ind.  fr  Engr.  Chem.,  Vol.   10,  p.  222,  Mar.,  1918. 
Blotting   Paper,   The   Testing   of,   by    P.    L.    Houston   and   R.    H.    Ledig. 

PAPER  TRADE  JOURNAL,  Vol.  73,  No.  19,  p.  88,  Nov.  10,  1921. 
Blotting   Paper,    Technology   of.     Paper,    Vol.   20,    No.    10,   p.    16,    May 

16,  1917. 

Bulker    Measuring  by  Perkins  Pressure.     Paper,   Vol.   19,   No.   4,   p.   86, 

Oct.  4,  1916. 
Bursting   Strength   of  Paper,   Conditions  Which  Influence  the,  by   D.  C. 

Douty.     PAPER  TRADE  JOURNAL,  Vol.  50,  No.  6,  271,  Feb.  10,   1910. 
Cardboard,   The   Testing   of— for    elasticity,    rigidity   and    folding,    by    R. 

Isnard.     Cham.    Abstr.,    Vol.    15,    p.    3205,    Sept.    20,    1921;    PAPER 

TRADE  JOURNAL,  Oct.  20,  1921. 
Chemical   Analysis   of   Paper,   by   H.   A.    Bromley.     Paper,   Vol.    15,    No. 

6,  p.  17,  Oct.  21,  1914. 
Cigarette    Papers,    Chemical    Analysis    of,    by    Strand    Jordan.     Jour,    of 

Ind   fr  Engr.  Chem.,  Vol.  8,  No.  9,  p.  812,  Sept.,  1916;  Paper,  Vol. 

19,  No.  10,  p.  13,  Nov.  15,  1916. 
Coated    Papers    &    Their    Constituents,    The    Manufacture    &    Technical 

Examination  of,  by  H.  A.   Bromley.     Pulp  and  Paper  Mag.  of  Can. 

Vol.  13,  No.  17,  p.  463,  Sept.   1,  1915. 
Color,  The    Measurement   of,   by   C.    E.    K.    Mees,   Jour.   Ind.   cr   Engr. 

Chem.,  Vol.   13,  No.  8,  p.  729,  Aug.,   1921. 

Color  Measurements.     PAPER  TRADE  JOURNAL,  July  8,  1920,  p.  58. 
Color     A    Means    of    Accurately    Matching    (Ives    Tint-Photometer),    by 

Otto  Kress  and  G.  C.  McNaughton.     Paper,  Vol.   18,  No.  21,  p.   13, 

Aug.  2,  1916. 

Color   System,  An   Examination  of  the   Munsell,  by  I.  G.  Priest.     Tech- 
nologic Papers,  No.  167,  of  Bureau  Standards.  > 
Dirt  in  Paper,  Identifying,  by   D.   M.   McNeale.     Paper,  Vol.    24,   folio 

p.   1058,  Aug.  20,   1919. 

Expansion    of    Paper,    Relation    of    Moisture    and    Paper,    by    E.    Suter- 
meister.    PAPER  TRADE  JOURNAL,   Vol.    59,   No.    27,   p.   44,   Dec.   31, 
1914. 
Fiber  Analysis,  Microscopic  Paper,  by  G.  K.  Spence  and  J.  M.  Knuiss. 

Paper,  Vol.  20,  No.  11,  p.  11,  May  23,  1917. 

Fiber  Analysis,  Paper.     Paper,  Vol.  17,  No.  3,  p.  19,  Sept.  29,  1915. 
Fiber    Board,    Effect   of  Varying    Humidities,    by    Otto    Kress   and   G.    C. 

McNaughton.     Paper,  Vol.  22,  folio  p.  251,  May  22,  1918. 
Fiter  Board,  Impact  Test  for,  by  E.  O.  Reed  and  F.  P.  Veitch.     Paper, 

Vol.  24,  folio  p.  923,  July  30,   1919. 
Fiber  Length  and  Position,  by  W.  Codlitz.     PAPER  TRADE  JOURNAL,  Vol. 

72,  No.  1,  p.  56,  Jan.  6,  1921. 
Fibers    as    Related    to    Pulp    and    Paper,    Structure    of    Wood    and    Sc.me 

Other,    by    H.    N.    Lee.     Pulp    and    Paper   Magazine    of    Can.,    \  ol. 

13,  No.  13,  p.  361,  July  1,  1915. 

Fibers.    The    Characteristics    of,    by    H.    A.    Maddox.     Pulp    and    Paper 
Mag.  of  Can.,   Vol.   13,  No.   21,  p.   551,  Nov.   1,  1915. 


44.  Fibers,   Differentiation   of  Jute,   Manila   and   Adansonia.     Paper  Makers' 

Monthly  Jour.,  Vol.  57,  No.  12,  p.  367,  Dec.  15,  1919. 

45.  Fibers,  The   Length   of   Some  Paper  Making,  by   E.   Sutermeister.     Pulp 

and  Paper  Magazine  of  Canada,  Vol.  12,  No.  2,  p.  43,  Jan.  15,  1914. 

46.  Fibers,   Factors  in  the  Measurement  of  Pulp,  by  J.   H.   Graff  and  Marie 

Hodgdon.     Paper,  Vol.  23,   folio  p.  333,  Dec.  4,   1918. 

47.  Fibers,  Length  of  Wood,     Paper,  Vol.  26,  folio  p.    15,  Mar.   10,   1920. 

48.  Fibers   in   Paper,    Estimating   Percentages,    R.    C.    Griffin.     Jour.    Ind.   & 

Engr.  Chem.,  Vol.  11,  No.  10,  p.  968,  Oct.,  1919;  Paper,  Vol.  25, 
folio,  p.  463,  Nov.  5,  1919. 

49.  Filter  Paper,  Testing.     Zcll  staff  u.  Papier.  Vol.  No.  1.  p.  61,  May,  1921. 

50.  Filter   Paper,  The  Penetrability  of,   by   R.   C.   Griffin  and  H.   C.   Parish. 

Jour,   of  Ind.   cr   Engr.   Chem.,  Vol.   14,  No.   3,  p.   199,   Mar.,   1922. 

51.  Filter  Paper,   Nctes  on  the  Testing  of,   by  J.  Rigand-Monin.     Papeterie, 

Vol.  42,  No.  — ,  p.  818  (1920). 

52.  Folding,    Resistance  to,  by   W.    Herzberg.     Chemical    Abstracts,   Vol     14, 

p.  2262,  July  20,   1920. 

53.  Folding  Endurance  of  Paper,  by  F.   P.  Veitch,  C.  F.   Sammet  and  E.  O 

Reed.     Paper,   Vol.  20,  No.   12,   p.    13,  May  30,   1917. 

54.  Gelatin  and  Casein.     Papeterie,  Vol.  42,  p.  122,  Feb.  10,  1920. 

5.i.     Glarimeter,  by    Kieser.     Zrllstofi    u.   Papier,   Vol.   1,   i>.    113,  July,   1921. 

56.  Glarimeter,    Instrument    for    Measuring    the    Glaze   of    Paper.      Electrical 

World  Vol.  63,  p.  645,  Mar.  21,  1914;  Pulp  S-  Paper  Mag  of 
Can.,  Vol.  12,  p.  233,  Apr.  15,  1914. 

57.  Glarimeter,   Improved,   by   L.    K.    Ingersnll.     Paper,   Vol.   27,   No.   23,   p. 

18,  Feb.  9,  1921. 

58.  Gloss  of  Photographic  Paper,  Measuring  the.     Paper,  Vol.  26,  folio  p.  782, 

May   26,    1920. 

59.  Graphic  Analytical   Method    for  Paper,   by  O.  L.  Gartland.     Paper,  Vol. 

25,  folio  p.  515,  Nov.  12,  1919. 

60.  Groundwocd,    Phenylhydrazine   Test    for.     Paper     Vol.    23     folio    p.    31, 

Sept.  18,   1918. 

61.  Humidity   Affects   Paper,   How,  by   H.   A.    Maddox.     Paper,   Vol.   7,  No. 

.22,  p.  4  (1911). 

62.  Humidity,  How  Paper  Is  Affected  by,  by  Otto  Kress  and  Philip  Silver- 

stein.     Paper,  Vol.   19,  No.  25,  p.   13,  Feb.  28,  1917. 

63.  Humidity,  Physical  Testing  of  Papeir  as  Affected  by,  by  Ross  Campbell 

Jour.  Ind.  &  Engr.  Chem.,  Vol.  9,  p.  658,  July,   1917. 

64.  Humidity   on   the   Moisture    O  ntent   of   Paper.     The   Effect    of,   by    Ross 

Campbell.     PAPER  TRADE  JOURNAL,  Vol.  73,  No.  2,  p.  30  (1921). 

65.  Humidity   on    the    Strength    of    Paper,    Effect    of    Papeterie,   Vol.    41     p 

455,  Oct.  25,  1919. 

66.  Humidity    Testing    Room,    Description    of   a    Constant    Temperature   and, 

by  F.  P.  Veitch  and  E.  O.  Reed.  Paper,  Vol.  21,  No.  23,  p.  174, 
Feb.  13,  1918;  Jour,  of  Ind.  cr  Engr.  Chem.,  Vol.  10,  p.  38,  Jan., 
1918. 

67.  Iron   Impurities   in    Paper,  by  H.   A.    Maddcx.     Pulp   cr  Paper  Mag.    of 

Can.,  May  1,  1914. 

68.  Laboratory,   Notes   on   the  Design  and    Equipment  of  a  Paper  and   Pulp 

Mill,  by  "Snow-Shoe."     Pulp  fr  Paper  Mag.  of  Can.,  Oct.  1,  1915. 

69.  Loading    and    Filling    Materials,    by    Sindall    &    Bacon.     Paper    Makers' 

Monthly  Journal;  Paper,   Vol.  20,  No.   7,  p.  22,  Apr.  25,   1917. 

70.  Loading  of  Paper,  Qualitative  Determination  of  the.     La  Papeterie,  Vol. 

41,  p.  266,  Aug.  25,  1919. 

71.  Microscope,    The    Use    and    Care   of   the,    by    E.    Sutermeister.     Pulp    fr 

Paper  Mag.  of  Can.,  Vol.  13,  No.' 22,  p.  576,  Nov.  15,  1915. 

72.  Microscopic    Analysis    of    Fibers,    Modification    of    Iodine-sulphuric    Acid 

Stain.     Paper,  Vol.  24,  folio  p.  707,  July  9,  1919. 

73.  Microscopical   Analysis  of  Fibers.     La  Papeterie    Vol.   41,   No.    1,   p    30, 

May  25,  1919. 

74.  Microscopical    Characteristics    of    Rosin,    by    James    Scott.      The    Paper 

Makers,  Vol.  49,  No.  6,  p.  671,  June,  1915;  Paper,  Vol.  16,  No. 
18,  p.  13,  July  14,  1915. 

75.  Microscopical    Examination    of    Paper    Fibers.     Paper,    Vol.    29,    No.    9, 

p.  25,  Nov.  2,  1921. 

76.  Microscopical   Work  in   Paper  Testing,  by  E.  M.  Chatnot.     Jour    of  Ind 

fr  Engr.  Chem.,  Vol.  10,  No.  1,  p.  60,  Jan.,  1918;  Paper,  Vol.  21, 
No.  19,  p.  17.  Jan.  16,  1918. 

77.  Microscopy,    Iodine    Solution    in    Paper,    by    C.    J.    West.     PAPER    TRADE 

JOURNAL,  Vol.  73,  No.  4,  Aug.  4,  1921. 

78.  Microscopy  of  Paper   Fiber   (C.   G.   Bright   Stains).     Paper,  Vol.  20,  No. 

25,  p.  11,  Aug.  29,  1917. 

79.  Microscopy  of  Parchment  Paper,  by  C.    Bavtsch.     Pupier-l-ahrikuiit     Yul. 

16,  p.  171   (1918). 

80'.     Microscopy  of  Pulpwoods,  by  Eloise  Gerry.     Paper,  Vol.  26,  folio  n.  277, 
Apr.  21,  1920. 

81.  Mineral    Matter    of   Paper,    Analysis    of,   by    J.    Scott.     Paper    Maker    &• 

British  Paper  Trade  Journal,  Vol.  t>l.  No.  4. 

82.  Moisture  on  Paper  Tests,  Influence  of.     Paper  Makers'  Mi  uthlv   U'unnif, 

Vol.  60,  No.  1,  p.  25,  Jan.   16.   1922. 

83.  Moisture    on    Paper,    Effect    of,    Paper    Makers'    Monthly    Journal,    Vol. 

57,  p.  231,  Aug.  15,  1919. 

84.  Moisture  on  Paper  Tests,   Influence  of.     Paper,  Vol.   29,  No.  4,   p.   16, 

Dec.  7.  1921. 

85.  Moisture  Regain  of   Papers  at    Different   Humidities,   liy  Otto   Kress  and 

G.  C.  McNaughtr.n.     Paper.  Vol.  22,  folio  p.  665,  Aug.  21.  1918. 

86.  Capacity,  Factors  in  Obtaining.     PAPER  TRADE  JOURNAL.  July  29,  1920. 
"87.     Paper  Microscopy,  by  J.  H.  Graff.     Paper,  Vol.  23,  folio  p.  642,  Feb.  12, 

1919. 

88.  Paper    Sizing,    by    Fritz    Stockigt.      Wochenblatt    fur    Papicrfahrikation, 

Vol.   1,   p.   39   (1920);    Paper,    Vol.   26,   folio   p.    Mar.    1O,    1920. 

89.  Paper  Testers,  by  D.  (     Douty.     PAPER  TRADE  JOURNAL,  Vol.  (HI,  \o.  6, 

p.  259,  Feb.  10,  1910. 


PAPER     TESTING     METHODS 


39 


90.  Paper  Teeing.      World's  Paper   Trade  Re-.'ieu;   Vol.   74,  p.   26,   Dec.  24, 

1920. 

91.  Paper  Testing,  by  F.  A.  Curtis,  Circular  No.   107,  Bureau  of  Standards. 

92.  Paper  Testing,   Report   of  Committee  of  Tappi,   by   F.    C.   Clark.     I'apcr, 

Vol.  21,  No.  6,  p.   11,  Oct.   17,   1917;  Paper,  Vol.  21,  No.  7;  p.   11, 
Oct.  24,  1917. 

93.  Paper  Testing,  TAPPI  Report  on,  by  F.  C.  Clark.     Paper.  Vol.  25,  folio 

p.  693,  Dec.  10,  1919;  Dec.  17,  1919;  Dec.  24,   1919;   Dec.  31,  1919; 
Jan.  7,   1920. 

94.  Paper   Testing,  The   Technique   of,   by    II.    A.    Bromley.     Pulp   &   Paper 

Mag.  of  Can.,  Vol.   U,  No.  16,  p.  439,  Aug.    15,   1915. 

95.  Phlorcgiucinol,  Notes  i.n  the  Chemistry  of.     Paper,  Vol.  22,  folio  p.  641. 

Aug.  14,  1918. 

96.  Photomicrographic   Study   of  Paper,  by   E.   A.   Hunger.     Paper,  Vol.   20, 

Xo.   19,  p.   14,  July   18,   1917. 

97.  Porosity  of  Papers,   Determining  the.     Paper,  Vol  22,   folio  p.   91,  Apr. 

10,  1918. 

98.  Porosity  of  Paper,  Method  of  Testing  Relative,  by  F.  J.   Seiter.     Paper, 

Vol.  21,  No.  2,  p.  17,  Sept.  19.  1917. 

99.  Pulps  in   Paper.   Method   for  Differentiating  and    Estimating  Unbleached 

Sulphite  and   Sulphate,  by   R.   E.   Lofton  and  M.   F.   Merritt.     Tech. 
Papers,  189,  "Bureau  of  Standards. 

100.  Qualities  and  Tests  of  Paper.     La  Papclcric,  Aug.   10,  1919;  Paper,  Vol. 

25,  folio  I>.  1112,  Feb.  11,  1920.        • 

101.  Qualities  and   Tests   of  Paper.     La   Papeterie,   Vol.   41,   p.   98,  June   25, 

1919.    Vol.    41,    p.    226,    Aug.    10,    1919;    Paper,    Vol.    ,25,    p.    1114 
(1920). 

102.  Quality  of   Paper,    Methods  of   Estimating  the,   by  F.   C.    Clark.     Paper, 

Vol.  10,  No.  /,  p.  15,  Jan.  29,  1913. 

1  o.i  Kt'sin  in  Paper,  Quantitative  Determination  of,  by  C.  F.  Sammet.  Jour, 
hid.  &•  Engr.  Chem.,  Vol.  5,  p.  732,  Sept.,  1913;  Paper,  Vol.  13,  No. 
1,  p.  17,  Sept.  17,  1913. 

104.  Rosin   Sizing,   An    Investigation   of,   by   F.   C.   Clark  and  A.    G.    Durgin. 

Paper,  Vol.  21,  No.  23,  p.  136,  Feb.  13,  1918. 

105.  Size-Fastness,   A   New   Test    for,   by    Stanley   A.    OkeJl.     Paper,   Vol.   20, 

No.  5,  p.  20,  Apr.   11,  1917. 

106.  Size-Fastness,  Okell's  Method  for,  by  S.  A.  Okell.     Paper.  Vol.  22,  folio 

p.  469,  July  3,  1918. 

107.  Size-Fastness    of    Paper,    Xew    Method    for    Determining    the.    by    Fritz 

Stockigt.      H'ochenblatt    fur   Papier-fabrikation    (1920);   Paper,   Vol. 

26,  p.   1    (1920). 

108.  Sizing,   A   New  Test   for,   by  C.  J.   West.     PAPER  TRADE  JOURNAL,   June 

24.  1920. 

109.  Sizing  with  Iodine,  Testing,  for.     Jour,  of  Ind,  &  Engr.  Chem.     Vol.  11, 

p.  972  (1919). 

110.  Sizing   in    High   Grade    Papers,    Detection   of   Faulty,   by    C.    F.    Sammet. 

Circular    No.    107,    Bur.   of   Chemistry,    Dept.    of   Agr.;    Paper,    Vol. 
10.  No.  9,  p.  15,  Feb.   12,   1913. 

111.  Sizing   of    Paper,    Research    Work   on    the,    by    F.    C.    Clark    and    A.    G. 

Durgin;  Paper,  Vol.  22,  folio  p.  223,  May  15,  1918. 

112.  Sizing  Quality,  The   Determination   of,  by   F.   T.   Carson.     PAPER  TRADE 

JOURNAL,   Vol.   74,  No.   14,  Apr.  6,   1922. 

IK1.  Soda  and  Sulphite.  Pulp*,  Differentiation  of,  by  P.  Klemm.  Wochschr., 
Papier-fabrikant.  Vol.  48.  No.  — ,  p.  2159. 

114.  Soda  and   Sulphite  Wood  Pulps  in   Paper,   Detection  of,  by  R.  Wasicky. 

Papier- fabnkaut,    Vol.    16,    p.    212    (1918);   Jour.    Soc.    Chem.    Ind., 
Vol.  38.  ( 

115.  Spots  in  Paper,  Soot   nr  Carbnn.      Paper,  Vol.   17,  No.   15,  p.    15,   Dec.  2-'. 

1915. 

116.  Staining  of  Wood  Fibers   for  Permanent  Microscopic  Mounts,  by  H    N. 

Lee.     Pulp  &  Paper  Mag.  of  Can.,  Feb.  1,  1917. 

117.  Starches — Properties  Useful  to   Mills,  by  G.   M.  MacNider.     Paper,  Vol. 

20,  No.    1,  p.    16,  Mar.   14,   1917. 

118.  Starch    in    Presence    of   Cellulose,    Determination    of,    by    F.    Kaulfersch. 

'.  him  e  ct    Industrie.   May,    1921. 

119.  Starch  in  Paj>er,  Estimation  of,  by  O.  Kamm  and  F.  H.  Tendick.     Paper 

Vol.  25,  folio  p.  460,  Nov.  5,  1919. 

120.  Starch    in    Paper,   Quantitative    Estimation    of,    by    V.    Voorhees   and    O. 

Kamm.     Paper,  Vol.  24,  folio  p.  1091,  Aug.  27,  1919. 


by  H.  N. 


123. 

124. 
125. 

126. 
127. 
128. 
129. 
130. 
131. 

132 
133. 

134. 
135. 
136. 

137. 
138. 
139. 
140. 

141. 

142. 
143. 
144. 

145. 
146. 
147. 

148. 
149. 

150. 

151. 

152. 


Staining  of  Wood  Fibers  for  Permanent  Microscopic  Mounts, 

Lee.     Bctanic'al  Gazelle,  Vol.  62,  No.  4,  p.  318,  Oct.,  1916. 
Strength  of  Paper  When  Wet,  Determining  the,  by  E.  O.  Reed.     Journal 

Ind.   &  Engr.    Chem.,    Vol.   8,    No.   — ,   p.    1003,   Nov.,   1916;   Paper, 

Vol.  19,  No.  11,  p.  15,  Nov.  22,  1916. 
Strength    Tests    for    Paper,    Description    of   a    Paper    Tearing   Resistance 

Tester,  by  H.  N.  Case.     Jour,  of  Ind.  &  Engr.  Chem.,  Vol.  11,  No. 

I,  p.  49,  Jan.,  1919;  Paper,  Vol.  23,  folio  p.  509,  Jan.  15,  1919. 
Sulphite   and    Soda   Pulp   in    Paper,  Test    for.     Paper,    Vol.   24,    folio   p. 

317,  May  7,   1919. 

Sulphite    and    Sulphate    Cellulcse    in    Paper,    Testing    Methods    for,    by 
C.   G.    Schwalhe.     Pulp  fr  Pn*er  Max.  of  Can.,  Vol.    12,   Nc,   1,  pp. 

II,  21,  Jan.   1,  1914. 

Sulphite    Pulps.     The    Differentiation    of,    by    T.    B.    Seibert    and    J.    E. 

Minor.     Paper,  Vol.   25,   folio  p.   1005,  Jan.   28,    1920. 
Sulphur  in  Paper,  Determination  of,  by  E.   Sutermeister.     Pulp  &  Paper 

Mag.  of  Can.     Vol.   15,  No.  44,  p.   1021,  Nov.  1,  1917. 
Tearing   Resistance  of   Paper,    Te  ting,   by    C.    F.    Sammet.     Paper,   Vol. 

25,  folio  p.  1053,  Feb.  4,  1920. 
Tearing    Resistance   of    Paper,    by    S.    D.    Wells.     Paper,    Vol.    23,    folio 

p.   750,   Feb.    12,   1919. 
Tearing  Resistance  Tester,   A   Paper,  by  H.   N.   Case.     Jour,  of  Ind.   cr 

Engr.    Chem..    Vol.    11,   p.   49    (1919). 

Tearing    Strength    of    Paper,    Supplementary    Study    of    Commercial    In- 
struments    for     Determining,     by     P.     L.     Houston.     PAPER    TRADE 

JbuRNAL,  Vol.   74,  No.    1O,  p.  43,  Mar.  9,  1922. 

Tearing  Strength  of  Paper.     World's  Paper  Trade  Review,  Vol.  75,  p.  6. 
Tearing    Strength    of   Paper,    Device    for    Testing   the    (U.    S.    Pat.    No. 

1,273,972),  by  R.  O.  Wood,  to  A.  D.  Little,  Inc.     Jour.  Soc.  Chem. 

Ind..   Vol.   37,   No.  21    (1918). 
Tearing   Strength   Test    for    Paper,    by    A.    Elmendorf.     Paper,    Vol.    26, 

folio  p.  302,  Apr.   21,   1920. 
Tensile  Strength  Tester    (T.  J.   Marshall  &  Co.).      World's  Paper   Trade 

Rez'ie-u.',  Vcl.  75,  No.  5,  p.  468. 
Tearing  Test,   Preliminary  Study  of  Tearing  and  Tearing  Test   Methods 

for    Paper    Testing,    by    P.    L.    Houston.     Tech.    Papers,    No.    194, 

Bureau   of   Standards. 
Testing  of  Paper  and    Paper   Products    for   Specific  Use,   by  J.   D.    Mal- 

colmson,   The  Paper  Industry,  Vol.   1,  No.  2,  p.  104,  May,   1919. 
Testing   Physical    Properties,   by    S.    W.    Widney.      The   Paper  Industry, 

Vol.  1,  No.  7,  p.  514,  Oct.,  1919. 
Translucent    Effect    on    Paper.    Photometric    Experiments   of   the.     Jour. 

of  Ind.  &  Engr.  Chem..  Vol.  9,  No.  — ,  p.   184,  Aug.,   1917. 
Translucency   and    Opacity    of   Paper,    Measuring   the,    by    R.    Fournier. 

Papier,  Vol.  23,  p.  259,   Nov.,   1920. 
Translucency    of    Papers,    A    Measurement    of    the,    by    C.    F.    Sammet, 

Circ.    No.    96,    liur.    Chem.,    Dept.    of   Agri.;    Paper,    Vol.    7,   No.    7, 

p.  22,  May  1,  1912. 

Transparency  of  Paper  and  Tracing  Cloth,  Specifications  of  the.     Circu- 
lar No.   63,   Bureau  of   Standards. 
Vegetable  Fibers   Used   in    Paper   Making,  by  F.   C.  Clark.     Paper,   Vol. 

23,   folio  p.  944,    Feb.   26,   1919. 
Volumetric    Estimation    of    Paper,    by    E.    H.    Hiarne,    Papier-fabrikant, 

Vol.  13,  No.  45,  p.  709,  Nov.  5,  1915;  Paper,  Vol.  17,  No.  20,  p.  14, 

Jan.   26,   1916. 
Water  Resistance  of  Fabrics,  by  F.  P.  Veitch  and  T.  D.  Jarrell.     Jour. 

Ind.  &  Engr.  Chem.,  Vol.  12,  p.  26  (1920). 
Webb  Paper  Tester,  by  J.  D.  Malcolmson.     Paper,  Vol.  23,  folio  p.  976, 

Mar.   5,   1919;   Jour.   Ind.  fr   Engr.    Chem.,  Vol.    11,   p.   133    (1919). 
Weight    of    Paper,    Determination    of    the    Apparent    and    Actual    Unit. 

Papier-fabrikant,   Vol.    17,   p.   472    (1919). 

Witham  Paper  Tester.     Paper,   Vol.   24,  folio  p.    156,  Apr.  9,   1919. 
Wool,   Test    for,   by    H.    LeB.    Gray,    Jour.    Ind.    &•    Engr.    Chem.,    Vo». 

10,  p.  633    (1918). 

Yellowing  of    Paper.     Paper,   Vol.   22,  folio   p.    1,    Mar.    13,    1918. 
Yell<  winp  of    Paper,   by   A.    P.    Hitchins.      Paper,   Vol.   22,    folio  p.   553, 

July  24,  1918. 
Zinc-Chloride-Iodine  Reagent  and  Its  Uses,  by  F.  C.  Clark.     Paper,  Vol. 

7,   No.   5,  p.   23,   Apr.   17,  1912. 


Page 
A 

Absorption   Test    25 

Acid  in   Paper    36 

Air  Volume  of  Paper   29 

Alcohol-Ether   Method    33 

Alum  Spots  in  Paper   16 

Analysis,    Chemical     31 

Analysis,     Microscopical     7 

Aniline  Sulphate  Stain   13 

Anti-Tarnish    Papers    35,  36 

Area  of   Sample    19 

Articles  in  Magazines   38 

Artificial   Illumination    11 

Asbestine    '. . .  32 

Ashcroft   Tester 22 

Ash  Determination   31 

B       . 

Balances     20 

Beater   Starch    35 

Beating,  Degree  of  16 

Bibliography    38 

Blanc  Fixe   32 

Blotting   and   Fillers 26 

Blotting    Paper 25 

Blotting    Test    26 

Books     38 

Breaking   Strength    23 

Breaking  Strength  and  Relative  Humid- 
ity      19 

Bright    Stain     13 

Bulk    21 

Bursting    Strength    20 

Bursting  Strength  and  Relative  Humid- 
ity  '.....  18 

Bursting  Testers,  Comparison  20 

Button  Specks  in  Paper  16 

C 

Calibration  of  Folding  Tester 22 

Carbolic  Aoid  in  Paper  36 

Cards,   Record    7 

Case  Tearing  Test  27 

Casein  in  Paper  33 

C.  G.  Bright  Stain   13 

'Characteristics  of  Fibers    14 

Characteristics  of  Paper  19 

Chart  of  Paper  Tests 8 

Chlorine  in  Paper  35 

Chrome  Yellow   36 

Classification  of  Fibers   . . .- 13 

Coal  Particles  in  Paper   16 

Coating,  Amount   of    32 

Coloring  Matter 36 

Color  Spots  in  Paper 16 

Common  Stains   11 

Compactness,  Relative   21 

Comparison  of  Bursting  Testers 20 

Composition,   Volumetric    29 

Conducting  Particles   30 

Conductivity  Method   '. 28 

Container  Board,  Tester  for  22 

Contrast  Ratio  26 

Conversion   Factors    20 

Conversion  to  Metric  System 20 

Count   Method   11- 

Cross  Direction   19 

Crown  Filler    32 

D 

Degree  of  Beating   16 

Degree  of  Sizing   •. ..  27 

Development  of  Paper  Testing 6 

Dextrine    '35 

Dirt   in    Paper    16 

Drag  Spots  in  Paper  16 

Dunlop  Method  for  Paraffin   32 

E 

Electrolytic  Method   28 

Elmendorf  Tearing  Test  27 

Elongation,  at  Rupture 25 

Estimation  of  Fiber  Content   7,  11 

F 

Factors,  Conversion   20 

Fats   in   Paper    •. 36 

Felt  Side  19 


INDEX 

Page 

Ferric   Ferricyanide    13 

Fiber  Analysis   7 

Fiber    Examination     7 

Fiber  Weight  Length  Method   7,  '. 

Fibers,  Characteristics  of   14 

Fibers,  Classification  of 13 

Filler    Retention    30 

Fillers,  Determination  of 32 

Fillers  and  Blotting 26 

Finish,  Measurement  of    28 

Flotation   Method    27 

Foam  Spots  in  Paper    16 

Folding    Endurance    21 

Folding  Endurance  and  Relative  Humid- 
ity  19,  22 

Folding   Factor    22 

Free  Acid  in  Paper  , 36 

Fuchsine  . . ' 12 


Glarimeter  Principle   29,-  30 

Gloss,  Measurement  of   28 

Glue  and  Casein   33 

Green  Folding  Tester    T 23 

Groups  of  Test  Methods   7 

H 

Herzberg  Stain 11 

Humidity,  Effect  of   17 


Ingersoll  Glarimeter   28 

Ink,  Standard,  for  Absorption  Test ....  25 

Interpretation  of   Data    37 

Iron  Specks  in  Paper  16 

J 

Jenk's   Stain   11 

K 

Kamm  and  Tendick   35 

Kamm  and  Voorhees  Method  34 

Klemm  Test   26 

Knife  Edge  Test   27 

Knots  in  Paper   16 

L 

Little  Tearing  Test    27 

Loading,  Retention  of  29 

Lofton-Merritt  Stain 12 

M 

Machine   Direction 19 

Magazine  Articles  38 

Malachite   Gr.een 12 

Manipulation  of  Fiber  Examination. ...  10 

Merritt  Sulphate   Stain 12 

Metric,  Factor  for  Conversion  of  Weight  20 

Microscope   Magnification    11 

Microscopic    Analysis    7 

Moisture  and  Relative  Humidity 18 

Mullen   Tester    50 

N 

Nitrogen  Determination    34 

O 

Ochres 36 

Oil   36 

Oil  Specks  in  Paper 16 

Okell  Method  27 

Opacity  Apparatus 26 

Opacity   Test    . . '. 26 


Paper  Characteristics  19 

Paper  Specks   16 

Paper  for  Electrical  Equipment 30 

Paper  Tests,   Chart  of 8 

Paraffin   32,  36 

Para-Nitro-Aniline  Stain   13 

Particles,   Conducting    30 

Pearl    Hardening    32 

Penetration,  Water  30 

Phloroglucinol   Stain    12 

Photometer,   Martins-Koenig    29 

Photomicrographs    28,  35 

Physical  Testing   17 

Pigments,   Natural    36 

Pipette  Test 25 


Page 

Polarimetric  Method   35 

Preparation  of  Slide   7 

Prussian   Blue    36 


Raspail  Reaction   33 

Ratio   Bursting  Strength  to  Weight 21 

Ream,  Standard  19 

Relative    Humidity,    Effect   of 17,  22 

Resistance  to  Water  Penetration 30 

Retention   of   Loading • 29 

Roll  Lengths 20 

Rosin 33 

Rosin  Extraction  Apparatus   33 

Rosin  Specks  in  Paper   16 

Rubber  in  Paper 16 

S 

Salicylic  Acid  36 

Sammet  Method 33 

Sample  Area 19 

Sample,    Test 7 

Sampling    7 

Scales    20 

Schopper  Tearing  Tester 27 

Schopper  Tensile  Tester 24 

Shaker,  Test  Tube 10 

Sizing,  Degree  of,  Test  Methods  of  De- 
termining     27 

Sizing  Materials 33 

Sizing   Quality 27 

Slide,   Preparation   of 7 

Slide   Holder 11 

Smalts    36 

Special  Materials,  Tests  for 36 

Special   Stains    12 

Specks  in  Paper 16 

Spence  and  Krauss  Method 11 

Stains,   Common 11 

Stains,    Special 12 

Starch    16,    34,  35 

Stockigt  Method 28,  31 ' 

Strength  Ratio  20 

Stress-Strain   Tester    25" 

Strip  Test   25 

Substance  Number   20 

Sulphate  Stain   12 

Sulphur  in  Paper   35 

Sutermeister's  Stain   12 


Talc  32 

Tarnishing   Test    36 

Tearing  Strength  and  Relative  Humidity 

.19,  27 

Tearing  Tests  26 

Tensile    Strength    23 

Tensile  Strength  and  Relative  Humidity  19 

Tensile  Tester   24 

Testing,  Chemical  31 

Testing    Microscopical    7 

Testing,  Physical  17 

Thickness   Tester 21 

Thickness  Tester  Variation  21 

Tissue  Paper,  Anti-Tarnish 35 

Tolerances  7 

Trade  Size,  Weight  in 20 

Trans'lucency   ' 26" 

Transparency    . 26 

U 

Ultramarine    36 

Unbleached  Pulp  Stain  13 


Volumetric  Composition   29 

W 

Warren,   S.   D.,   &   Co.    Retention    For- 
mula      30 

Water  Penetration    30 

Webb  Tester  for  Container  Board 22 

Weight   19 

Weight  and  Relative  Humidity 18 

Wet  Tensile  Strength 24 

Wire  Side   19 

Witham  Tearing  Tester 27 

Wood  Specks  in  Paper 16 


Publications  of  the  Technical  Association  of  the  Pulp  and  Paper  Industry 

18  East  Forty-first  Street,  New  York,  N.  Y. 
Technical  Association  Papers,  Series  III,  1920.    In  paper,  60  pages,  $2. 


Tests  for   Unbleached  Sulphite  and  Sulphate  Fibers,  by  R. 

E.  Lofton  and  M.  F.  Merritt. 
Standard  Specifications  for  Cement  and  Lime   Paper   Bags, 

by  Paul  L.  Houston. 
Use    of    Sulphur    in    Soda    Pulp    Cooking,    by    ( iec >rge    K. 

S  pence. 

Substitutes   for   Alum  and  Rosin,   by   VV.    K.    Byron    Baker 
Substitutes  for  Alum  in  Papermaking,  by  Max  Cline. 


Automatic  Cooking   Control   lor  Chemical   Pulp,  by    C.  H. 

Allen. 
Automatic.  Mixing  System  for  Paper  Stock,  by   Edward  J. 

Trimbey. 

A  New  Felt  Cleaning  Device,  by  C.  A.  Woodcock. 
Fireproof  Hood  for  Paper  Machines,  by  F.  M.  Williams. 
Description  of  Emmet's  Mercury-Vapor  Boiler. 


Technical  Association  Papers,    Series  IV,  1921.    In  paper,  129  pages,  $3. 


How  to  increase  the  Efficiency  of  Water   Power  Plants,  by 

diaries  M.  Allen. 
Strength    Testing    of     Soda     Pulp,     by     Ralph     Mair    and 

Grellet  N.  Collins. 

Steam   Economy  in  Drying  on  and  Driving  of  Paper   Ma- 
chines, by  R.  W.  Leeper. 
Burning  of  Pulverized  Fuel  in  Paper  Mill  Power  Plant 

Loren  L.  Hebberd. 
Shortening  Cooking  Time  by   Preliminary    Impregnation  in 

the  Production  of  Sulphite  Pulp,  by  Vance  I'.  Kdwardes. 
Measuring  Moisture  of  Chips  in  Williams. 

Economics    of    Paper    Mill    Ki  ion,    by    Stephen    A. 

Staege. 
The   Fulton    System    for    Drying    of    Paper,    by    William   B. 

Fulton. 
A  Xew  Weightometer  for  Soft  Stock,  Chips  and  Acid,  by 

E.  /.  Trimbey. 


The  Effect  of  Variables  on  Bleaching  Efficiency,  by  George 
K.  S  pence. 

'Briner  Economi/er  I'Miig  Only  Waste  Heat  for  Ventila- 
tion of  Machine  Room,  by  W.  H.  Howell. 

Kintnaii  Modification  of  Sulphate  Process,  by  Bror.  N. 
Segerfelt. 

Manufacture  of  Ground  wood  by  the  Hrtll  Process,  by  W.  A. 
Munro. 

Evaluation  of  Lime  by   Causticizing  Test,  by  Carl  Moe. 

A  Simple  Moistun  iper,  by  C.  B. 

Whwing. 

Study  of  the  Casein  I  Paper,  by  Clarke 

Marion. 

Analytical  and  'rthods  01  littee  on  Stand- 

ard Methods  o  Materials,  by  E.  C.  Tucker. 

The  Analysis  of  Sulphite  Cooking  Acid,  by  Erik  Oman. 

Control  Analyses  of  Sulphit'-  I'rof.  Dr. 

Peter  Klason. 


Technical  Association  Papers,   Series  V,  1922.     In  paper,  170  pages,  $3. 


The  Power  Plant  of  the  Paper  Industry,  by  A.  G.  Darling 

and  H.  W.  Rogers. 
A    System    of    Records    to    Maintain    I'nitonnity    of    Basis 

Weights  of  Paper,  by  Parker  K.  Baird. 
Hydrating    Machinery    for   th.  Mill,    b>    George    L. 

Bidwell. 
Modern  Lighting  for  Paper  and  Pulp  Mills,  by  J.  H.  Kur- 

lander. 
Some    Factors    Influencing    Yield    and    Strength    of    Pulp 

Cooked  by  the  Soda  Process,  by  Martin  L.  Griffin. 
The   Efficient   Production   of   Mechanical    Pulp,   by    Adolph 

F.  Meyer. 

Sedimentation  Control  of  Groundvvood,  by  W.  A.  Munro. 

Drying  of  Paper,  by   M.  B.  Littlefield. 

The    Electric    Steam    Generator,    by    Horace    Drever    and 

Frank  Hodson. 

Recovery  and  h  G        ;<•  K.  Six.-'. 

Relative  Efficiency  of  the  Automal  •'••m-  Grinder  as 

Compared   with   the  Pocket   Type  Grinder,   by   John   J. 

Stamso — Cotton  Linter  Pulp,  by  Stewart  E.  Seaman. 
Recommended  Specifications  for  Limestone  and  Lime  in  the 

Manufacture  of  Sulphite  Pulp. 
Analysis  of  Reclaimed  Cooking  Acid  for  Sulphite  Mills,  by 

Gosta  P.  Genberg. 
Concerning    the    Analysis    of    Raw    Sulphite    Acid,    by    Dr. 

Rudolf  Sieber. 
Contribution  to  the  Knowledge  ••nstitution  of  Spruce 

Wood  Lignin,  by  Dr.  Peter  K!  i 
Concerning    Ligiiin    and    Lignin     K'.  by    Dr.    Peter 

Klason. 
Contributions  to  a  More  Exact   K>  if  the  Chemical 

Constitution  of  Spruce  Wood,  by 
Use  of  the   Continuous   Centrifugal,   by   J.    R.    Kessler   and 

G.  \".  Collins. 

The  Chemistry   of  the   Sulphite   Pr..  R.    N.    Miller 

and  W.  H.  Swanson. 


Report  of  Committee  on  Standard  Methods  of  Testing  Ma- 
terials, by  N.  F.  Becker. 

Color  Effect  of  Rosin  S  ion  on  Finished  Product, 

H.  Kent. 

Sulphur  in  Sulphite  Waste  Liquor.  Barsky. 

Producing  Bleach  Liquor  with  Liquid  Chlorine,  by  S.  W. 
Jacobs  and  H.  P.  Wells. 

The  Value  of  Fuel  Economi/  Mill  Operation, 

by  George  E.  Willi.  -rry. 

A  Mew  Idea  in  Chip  Break 

Paper  Tes" 

i    Paper. 

t  of  Relative  Humidity  and  Variation  of  the  Burst- 
ing Test. 
!  est. 
Sizing  Quality. 

Committee  on  Paper  Testing. 

Standard  Methods  of  Materials: 

Aluminum   Sulphate. 

•  u-ii  Filler. 
Lira 

Dyestuffs : 

of  Auramine. 

"Pix-r  Sul;-' 
Two-Side 
Stilbene  Yellow. 

Methods   • 

.iifd. 

Heat    :  rally   Required. 

Meat   Supplied. 
Graduation   of  Temperature. 

Pound-  of   P.'i         •  *)rying  Surface 

per  I  I 


Address  the  Secretary  Technical  Association  of  the  Pulp  and  Paper  Industry,  18  East  41st  St.,  New  York 


Publications  THE  Technical  Association  ™  Pulp  and  Paper  hdnstry 

18  East  Forty-first  Street,   New  York 
Technical  Association  Papers,  Series  VI   (1923).    In  paper,  208  pages,  $3 


A   Theoretical  Discussion   of  the  Reactions 

Papermaking:  Jessie  E.  Minor. 
Anti-Friction  Bearings:  G.  H.  Spencer. 
Bibliogr«~~ "~ 

West  ; 
Chemistt 

esses: 
Chemist! 

and  W 
Discussic 
Drying 

J.  O.  1 
Effect  o 

Tests: 
Efficienc 

W.  F. 
Evaporal 
Lake  C( 


of 


Manufact 


Methods  of  Establishing  Wage  Rates  and  De- 
termining Promotions:  H.  P.  Carrnth. 

Papers  on  various  subjects: 

Paper  testing;  several  papers. 

Reports  of  committees. 

Steam  Economy  in  Pulp  and  Paper  Mills:  E.  P. 

Gleason. 
Steam  Flowmeters  on  Sulphite  Digesters:  W.  H. 

Kraske. 

Study  of  Papermaking  Materials:  A.  B.  Green. 
Use  of  White  Water  in  Mechanical  Pulp  Mills: 

W.  E.  Brawn. 

Ventilation  of  Machine  Rooms:  J.  O.  Ross. 
Waste  in  the  Industry.  R.  B.  Wolf  and  G.  D. 

Bearce. 

White  Water  Losses  and  their  Correction. 
Utilization  of  Barking  Drum  Waste. 
Reduction  of  Broke  Losses. 


volumes.    In  cloth,  $5  per  volume. 

i:me  IV: 
Preparation    of    Rag    and    Other 

Fibers. 

Treatment  of  Waste  Papers. 
Engine  Sizing. 
Loading. 

Beating  and  Mixing. 
Coloring. 
Paper  Machines. 

Volume  V   (in  preparation)  : 

Tub  Sized  Papers. 

Finishing  Operations. 

Coated  and  Other  Treated  Papers. 

Manufacture    of    Special     Papers, 

Boards,  etc. 
Paper  Testing. 
Mill   Organization. 
General  Mill  Equipment. 
Dictionary  of  Papers,  Tables,  etc. 


Paper  Testing. 
Microscopical 


;vised  1922).    In  paper,  $3 


ang. 

alysis. 


Interpretation  of  Data. 
Bibliography. 


Folder  for  Technical  Association  Section,  25  cents.  Each  Folder  will 
accommodate  the  Section  pages  for  three  months. 

Index  to  Technical  Section,  Paper   Trade  Journal,  10  cents  each 


Address  the  Secretary 

Technical  Association  of  the  Pulp  and  Paper  Industry, 
18  East  41st  Street,  New  York 


PAMPHLET  BINDER 
Syracuse,  N.  Y. 


Stockton,  Calif. 


